I stumbled across the above link that features bands that have appeared in video games.
Got to the Johnny Cash section and noticed this :
Johnny Cash, Guitar Hero 5: After appearing in this game amongst other big music names and performing 'Ring of Fire', Johnny will also soon be getting his own game. Johnny Cash tribute artist Terry Lee Goffee has provided the movement for the legendís motion-capture.
Doesn't mention if it is for Rock Band or Guitar Hero, but I thought I'd share