I'd test for you, since there's an alu iMac at work, except all my -RAM discs are the caddy-only kind. I agree with kuebby that the chances are pretty slim, but it's not quite fair to call it a dead format. Not common, definitely, but most of the DVD burner mechanism manufacturers support DVD-RAM--Sony, Lite-on, Samsung, Plextor, LG, Phillips all have DVD-RAM-supporting drives, and even Pioneer's newer Blu-Ray reading drives do (outside case, I assume). All tray-load, though--not sure about slot-load drives.
Anyway, probably won't write, probably will read (don't most drives now?), but sticking one in is the only way to really be sure, even if somebody else tests it for you, since Apple may be using more than one brand of drive for the same model.