Valve Plans To Have Cross Platform Co-Op Between PS3 & PC/Mac

[makingmusic476]

Oh sweet.  So I can still play with my ps3 friends.

I wonder how this will work with Steamworks.  Will you have to use a Steam account on ps3?  Or will PSN accounts be incorporated into Steam?  Or will they simply allow both account types to access the same lobbies?  Last option seems the best.