I think that, "at the end of the day", once every Dallas County city or agency that intends to migrate to NTIRN completes their move, the SWRCC cities should be a separate group, not lumped together with others.
Looking at the Tarrant County side for a pattern, note that there is a specific "Combined Dispatch" category for North Richland Hills, Richland Hills, Haltom City, & Watauga. Those four cities share a set of talkgroups, rather than having their own individual TGIDs. I would think that the SWRCC cities, which also share a specific set of talkgroups, not individual ones, and are dispatched by one common PSAP, should be a specific department..
Now, for the Northeast Tarrant layer, there are also 'combined dispatch' talkgroups for PD & Fire in Colleyville, Keller, Southlake, & Westlake, but there are also separate TGIDs for each city for public safety. Those are all lumped into the Northeast Tarrant group, which also has all the assignments for the other NETCO cities, including the larger ones such as Bedford, Euless, & Grapevine..
Lancaster also, I would think, should also be a separate department. Lancaster's population, over 40K, is more than three times that of Forest Hill, which is a stand=alone department within the Tarrant County cities.
The unknowns, so far, are when (or if) Hutchins & Wilmer switch over. For now, Cockrell Hill is keeping their traffic on the Dallas Simulcast layer of the Dallas P25/NCTCOG system.
