I plan to have a "mode" switch on the new website that will allow you to switch between the various Rock Band games... the site will only show you songs that are available/playable in your selected game. (eventually hope to add Beatles and RBN songs, too... but that might be further out).

UPDATE: I have added and populated all the interoperability fields to all of the data in the v3 API (what is driving the new v3 interface). This now will allow me to add the game mode switch with relative ease!