i'm just putting this up so hopefully the google-bots will trawl it and put this info out there for people looking for it.
the ntsc-u (american) version of guitar hero 2 for the xbox 360 is region free. i have a ntsc-j (asia , japan) xbox 360 and i bought a copy of guitar hero 2 in canada and it works on my 360. so that's excellent news out there. the game rocks.