I have heard something similar up North on TG10250. A mix of 99xxxxx, 20xxxxx, and 71xxxxx radio IDs. The "20" radio ID also showed activity on Elkhart City and County PD talkgroups. The "71" radio IDs were also active on the St Joe County PD talkgroups. I haven't been listening to this TG this week to hear the recent traffic but have just been capturing activity all week using Unitrunker. Last time I did listen to 10250 it sounded like a stake out looking for a particular suspect so probably similar to what you are hearing on 10249.
I also saw TG10242,10243, and 10377 pop up. Logs show TG10242 was all encrypted comms with 99xxxxx radio IDs. 10243 and 10377 were just a 99xxxxx radio ID affiliating with it a couple of times but no voice traffic so no idea what those might be.
I have identified a bunch more unknown talkgroups that seem to be related to something in St Joe County based on the radio IDs affiliating with them. Traffic has been limited or not verbose enough to identify at least when I have been listening (short 1 or 2 word comms with no IDing at all except maybe using each others first names) so I have not been able to figure out what they are. Some of them have had radios affiliate with them but have had no voice traffic at all. If anyone else wants to program them in and see if you can catch any traffic and figure out what they are here are some of the talkgroup numbers:
12256, 12568, 12570, 12577, 12586, 12588, 12589, 12590, 12591, 12594, 12595, 12596, 12597, 12598, 12601, 12602, 12603, 12608, 12609, 12613, 12615, 12617, 12618, 12620, 12621, 12622
12599 and 12600 do appear to be Mishawaka Utilities Electric department and 12606 had Mishawaka City plows on it the last significant snow so that is probably the Mishawaka Street department. I'll officially submit those 3 for you and a couple more changes as well.
Brian