Chuck,
Are you seeing this on the new system?
I haven't been able to receive anything on the Chesapeake system, which tells me everything is phase II, but the database here says the only talk groups listed as phase II are the Regent University (CBN) police. Can you confirm whether or not it's all phase II (except for what you're seeing)?
Other than that, I have heard of phase II systems that will automatically switch a talk group to phase I if someone affiliates in that mode as Mike says. Usually a user from a neighboring locality.