Incidentally we are not simply limited to active or passive; in classical Greek there was a 'middle' voice too, meaning to do something 'for one's own behoof'; in Latin there are 'deponent' verbs - passive in form but corresponding to an active form in English.
In English we but seldom change distinguish some of these changes in meaning; 'The concert began' and "He began his homework" show no change in the form of the verb; however in other languages this might be two different verbs each with more specific meaning.

Nothing to stop a verb having more than one meaning, or the meaning changing slightly according to context, and varying between transitive/causative and intransitive:

Children grow quickly.
Flowers grew on the trees as summer approached.
He grows peppers and squash.
The boy grew wise as he matured.
Peppers and squash were grown in the allotment.
The trees grew flowers as summer approached.

Secondly, an idea may be typed as passive in one language but typed as active in another:

Opening of the Knight's Tale:
" Whilom, as olde stories tellen us
Ther was a duc that highte Theseus;"

"highte" is active in form but means "to be called" (cf heissen in German)

"I miss you" in English is expressed in some other languages as "You are missing for me".

So one cannot make rules about what should be passive or not.

"It's /It was pouring" seems to outtick "raining cats and dogs".

@SL

http://en.wikipedia.org/wiki/Ergative_verb

http://en.wiktionary.org/wiki/Category:English_ergative_verbs

"Transform" is there on the list of so-called ergative verbs.

I must confess when I first came across this stuff, it took me months to get to grips with it all; but in fact it is rather important when teaching English to speakers of languages where the passive either just exists not, or works not in the same way as English.

Enjoy.

@SL I think quite a number of style guides suggest that one should avoid the passive wherever possible.
There are still a few verbs pairs in English (like rise/raise, fall/fell) where the causative transitive is marked, but for the most part we do not mark it in English; thus we say:
a) "Interest rates increased" (somehow by themselves)
b) "Interest rates were increased" - (someone/thing caused them to rise)
What has happened here with "transform" is that the writer has applied the same (ergative) approach to avoid a passive: no reason why not, although it may be new to some of us.

A similar thing happened in Hungarian, and under pressure from style gurus the passive has all but disappeared from modern Hungarian (it remains only in the verb for 'to be born'); the 'ergative' forms are often distinctly marked. The end result is that professional Eng->Hung translators are often left scratching their heads when faced with an English passive; this is why I believe that those who preach that the passive is to be avoided at all costs are misguided: it is there to be used as and when needed, but not to excess.

@AnWulf The surgery in question used to be a couple of doctors in a rather homely converted detached house; now they have merged with others into a new clinic with a largish reception area and a fair walk to the subwait area - the first visit they escort you there in case you get lost. After all, there's a dozen consulting rooms, and other places for minor surgery and so on. I guess that's why they need the designation and signage 'subwait area'.
I suppose they could say 'go down the corridor, turn left and wait outside door number nine';
the old homey place was more personal was less impersonal though.

@WW
"If I repeat the point about usage, it is because this is one of the few language forums where this is not considered important."

Where is your evidence for this? ;=))

Sadly many normal, common or garden people believe their own opinions and are left unswayed by overwhelming evidence to the contrary. Vlad the Impaler, Tony B, Slobodan are names that spring to mind as examples.

sic transeunt populi anglici linguae gloriae

@Jasper Perhaps the root of the problem in English lies in the word roots:
http://etymonline.com/index.php?allowed_in_frame=0&search=this&searchmode=none
http://etymonline.com/index.php?allowed_in_frame=0&search=that&searchmode=none

"This" and "that" seem etymologically to be neuter and cannot refer to people as a pronoun.
I guess that is why we say not "It depends on that, who sits there." The outcome is that we search for another word and come up with "person", so in that way "It depends on the person sitting there." is NOT avoiding the issue - it is the true grammatical way of saying it - since we have, if you wish, no demonstrative pronoun for one person - it is a lost inflection.

@Jasper Not sure I can help you here; in truth I am not very academic. However FWIW in German ( and up till William the Bastard et al came to stay English was germanic) one would say something like:

A) Who am I, that I should judge? (well actually more like: Who am I, that I judge should?)
B) Whom should I judge?
C) I want that she go.
D) Who is he, that he me tells, what I do should?
E) Who am I, that I thus treated am? or Who am I, that they me like this treat?

Perhaps you might also ponder:
F) It hangs therefrom, who it is. (It depends on who it is. Or "It depends on whom it is").
G) It comes thereon, what was said. (It depends on that, which was said.)

Sentences F/G shows the conflict in English and how other Euro languages like German, Russian, Hungarian operate so there is no issue - one must always put in "therefrom", "thereon", or whatever.

We do something similar in English with sentences like:
Those whom God hath joined, let no man put asunder.
He who dares wins.

English had lost many inflections since 1066 (and before) so what we have left are often unneeded to put across the meaning. We use word order instead, so that "John hit his wife" is meaning-wise the reverse of "His wife hit John", and "John his wife hit" would might mean John got beat up (OSV), but might be SOV. (In Russian the inflections make it clear either way). But in Englsh we only really have I/me, he/him, who/whom, this/these,that/those to play with.

The telling point is that "this" and "that" do not usually refer to a person in English, whereas "those" often does. This leads to conflict as in:

H) It depends on whoever is sitting there.
I) It depends on whomever is sitting here. (I would mark this wrong)
J) It depends on the person sitting there. (common way to avoid the issue)

In Russian one might say something like:
k) It depends on that, who is sitting there. (where "that" is inflected to show it is a person)

Hope this helps