While that sounds like what Harmonix is doing with “Rock Band” clarification that we got from Sony shows it’s a bit different. You’re not exporting the music.
Instead, Sony is implementing a disc-swapping feature that was already present in some UK versions. Users just press select, pop in any PS2 “SingStar” disc and those songs drop into the PS3 version. The songs are not permanently brought over to the PS3 game, however. If you want to sing them, the PS2 disc needs to be present.
Worries that non-backwards compatible PS3s couldn’t use the new feature have been averted. Sony says a free patch for the current “SingStar” is coming this year and disc-swapping will be present on all future “SingStar” releases.