Sound Proofing P&M for a recording studio ?

I have just been to see a new client who has set up a recording studio.

He took over a bare industrial unit and created a couple of boxes inside with partitions & ceilings about a foot thick with insulation to form sound-proof recording studios. 

One room is where the musicians perform and the other is where all the recording equipment is and the sound must not bleed over from one room to the other - there's also a window in between (you've seen the sort of thing on the telly).

Question is, are these studios (the timber, plasterboard, insulation, paint, glass etc) providing a function (as opposed to just being the "setting") and can CA's then be claimed on the expenditure of creating them ?

I personally think they do provide a vital function, as it would not be possible to function without the acoustic control and the segregation of the sound (imagine what it would sound like if it was just recorded in an empty industrial unit !) and the setting doesn't really matter as it's not like they are trying to create an ambience or anything.

I look forward to other people's views on this.

Thanks.