At last night's Activision non-E3 press conference, it was quickly mentioned that Guitar Hero: World Tour being compatible with non-Guitar Hero instruments. Meaning? The Xbox 360 version of Guitar Hero: World Tour are compatible with instruments from the first Rock Band. (Obviously, the developers haven't been able to incorporate the unreleased Rock Band 2 instruments into the game.) While other third party guitar and drum controllers should jive with World Tour, Activision isn't yet commenting whether or not the Wii, PS2 or PS3 versions of both Guitar Hero and Rock Band will work with Guitar Hero: World Tour.
Activision: ‘Guitar Hero: World Tour' Is Compatible With ‘Rock Band' Instruments [Multiplayer]