9To5Mac reports that the new files are "radio buy" buttons that resemble the "radio play" buttons that already exist in iTunes. (Although, notably, the iPad's Music app doesn't have radio yet.)
The button files would seem to indicate that the Pandora-like service that is rumoured for launch in the first quarter of this year would offer some functionality so you could buy the songs that came on over the radio.
Given that Apple uses iTunes to sell music, this feature would be a totally obvious addition. This could all be hogwash, of course, so let's wait and see what Apple announces. [9to5Mac]