I heard it once near DNT and Lebanon in Frisco. While Frisco ISD is also on that same frequency (Wakeland HS), wrong Color Code (Wakeland is CC 5 TG 36).
Based on the license, I suspect its Methodist Hospital security (WQBD830) in Richardson (Bush Turnpike and Renner Road, East of Central Expressway), but that needs verification.
Dallas ISD has a license (WRJI629) for trunked usage, but that is down near Seagoville, and unlikely you'd hear it from North Dallas.
Finally, Azle Communications has a license (WPMM478) for that frequency for non-trunked use in Downtown Dallas, but the emissions designator is for Narrow FM Analog (but I typically don't trust that because I've seen a lot of DMR systems that the license has not been updated).