We've been discussing this over at ScanCobb.com. It is, indeed, Douglasville PD. The Cobb analog system had some backup talkgroups for Douglasville, and Douglasville's TRS had the same for Cobb, both to be used in the event of a major outage on the agency's home system, IIRC. So it could be for that. There was some additional talk on ScanCobb that Douglasville PD had been issued new digital radios, so maybe they're joining the statewide TRS that Cobb's system is a part of. Time will tell, I suppose.