The only thing I could find was a thread in the Playstation area about this.

Can anyone confirm if the Xbox 360 wireless guitar is going to work with Rockband?

yes the les paul guitar works with rock band but the RB guitar does not work with Guitar hero 3.

Thank you! :)

http://ps3.ign.com/articles/830/830792p1.html

It also lacks the solo buttons on the fret. No idea how this factors into gameplay, though.