Listened to an unknown TG, TG 51408, last night on the Aiken tower. Can't divulge what it was, but the conversations were very interesting. Started a little after 2300 and was still going at 0130 when I went to bed. It was P25 by the way.
51408 is in the RR database - LE Common 12. As the name implies, it's a shared interop talkgroup for law enforcement use, could pop up anywhere in the state at any time. And yes, it's designated as a digital talkgroup.
I heard the same thing here in Elgin on the Camden tower. Asked a co-worker at work if he had heard anything through the grapevine and he said no. Made for a very interesting late sunday night early monday morning listening.