Here’s the page on embedding CC into MP3:

http://creativecommons.org/technology/embedding

They don’t recommend embedding the license RDF in the MP3 metadata. Rather, they recommend embedding a link to a site you control with the metadata resident there. This approach is clearly problematic for adding to the Zune firmware, but makes sense for existing players, that are usually partnered with a jukebox on a desktop system.

The Wired article admits that verifiable CC metadata on the Zune would be problematic. Doesn’t look like anyone has offered any concrete suggestions, yet.