I think talkgroup activity will only occur locally (if you have no other users on that talkgroup affiliated with the site you are on, you've got no one to talk to). I think you can probably "roam", but there isn't going to be some graceful handoff by the system since the rest of the system doesn't know about you. Then again, I know zilch when it comes down to it. Maybe the sites themselves that are peers of each other talk to each other without access to the zone controller. I'll be interested to hear what somebody who really knows says