We know for certain that it is possible to include ALL the communication features of Live in a game for the PS3 (minus sending voice messages at this current time), but the developer has to code for that link to the XMB functionality.
This is true, but it currently takes 16 megs of memory to use the PS3 libraries. Right now that memory is being used for other goodness.
That said, development is on-going. And we are always working to improve things.
I'm glad to see everyone is excited about the game -- even if it has been released early in different places.