well, basically, you could fit any wheel on any car as long as you get the correct PCD adapters and as long as your car has wide fenders. ;)
e. g. SCC (www.spurverbreiterung.de) builds such adapters which, basically, are just spacers with two different PCD's.
BUT ... the big problem is: these adapters/spacers increase, of course, the final offset.
and the big Audi/BMW/... wheels, e. g., already have a large width and low offset, so even if you get the correct adapters, i'm sure the IS's fenders would not cover the wheels anymore.
regarding the bore size, you can simply buy adapters on the net or, if you have the possibility, ask a buddy that can build you some using a lathe.
sorry for my bad english!