Quoted from J85M:
Wouldn't the licensing be for the GOTG film and all it's content? Disney obviously licenced everything for the film so would that not put all the music under the same umbrella?
Doesn't work that way. Disney wouldn't have the right to transfer the license for each song to a third party. Would have to be relicensed from the original artist (or record company depending on who owns the rights). Even actors in the movies have to generally sign off on their likenesses being used.