Check out this forum page: http://www.guitartricks.com/forum/forumdisplay.php?f=58
Here you can request your songs. Only problem is that GT has to pay a license to be able to teach these songs legally. I think it will also cost GT a whole lot when they want to be able to teach GnR or Led Zeppelin.
Ofcourse a lot of people want to learn them but GT can't teach them for free. Check this page for some extra info: http://www.guitartricks.com/forum/showthread.php?t=34594
Hope that helps.
JJ