The project is currently in beta with availability set for some time around June, smack in between the May release of Digium's Business edition of Asterisk B.1 and the next rev of the public Asterisk 1.4 release in July.
I'm so incredibly excited about this project for lots and lots of reasons. Inter-company collaboration will become a lot easier now for Asterisk users. Extending out the Asterisk network is a cinch and think of all of the cool applications one could create for GoogleTalk. Heck, just real termination becomes easier.
But I get ahead of myself.
One of the things that's always puzzled me is why Google didn't just support SIP or even Mark's own IAX protocol used in Asterisk. Mark had the same question until he studied Google's SIP replacement, Jingle