Tonight I've been hearing what sounds like perhaps National Guard internal communications downtown on TG 19310 on the Atlanta system, given various references to humvees. The guard is still coordinating with APD on MA1, but perhaps also communicating among themselves on 19310. OTOH, I have also heard instructions to drivers of ATVs, including shortly after APD mentioned asking the Georgia DNR ATVs to handle a particular assignment, so perhaps this is DNR officers. It makes sense that DNR might borrow Atlanta radios given (I presume) they lack repeater coverage of their own downtown.
I have heard 19310 and 19311 used the last month or so for coordination of Covid testing sites and other such one-off activities, so I wonder if these talkgroups are programmed into radios that are in a cache that is handed out for temporary use at special events and the like.