1UP put on their investigating shoes and -- burrowing through the official forum -- found such a confirmation from Rock Band development member, Jason Booth. Debunking a (now edited) IGN article, Booth says, "For some reason, IGN posted that Rock Band will not be compatible with Guitar Hero guitars. I thought I'd drop in and let you know that this is not correct." Sweet, delicious vagueness.
So exactly which guitars will you be using to rock? We already know that PS2 guitars won't work on the PS3 without an adapter and said adapter has been deemed "impossible" by the manufacturer. The only other candidate is of course the Xbox 360 controller which, along with the newly endowed effects pedal port, makes it the clear winner in this situation.
For PlayStation 3 owners and those who don't plan on picking up the recently released Guitar Hero II for the 360, GameStop has come up with a list of speculative prices for various sets of Rock Band. Though nothing regarding prices or even separate packages have been discussed, seeing the numbers already has us tugging at the collar.