I've been listening to what sounds like digital audio on a BWI TAC TG on the AACo TRS. Maybe some BWI Fire units are transmitting on the MAA TRS, and that TG is being patched to AA Co's analog system? The BWI dispatcher sounds like pure analog.
BWI has a patch up for surrounding jurisdictions -- I was watching the call earlier tonight and saw the radio ID on the BWI system was the same for all non-BWI units. There is a similar reverse patch on the AA County TRS.