See the above posts by Mr. Lovell who is also in the radio profession.
So, I'm in the Fire Service Profession. ...don't want to be misrepresented here. I am one of the rare public servants that understands the radio systems we use and what the radios are capable of, making me appear to be an expert with my peers. ...but in no way can I think that I am a professional radio technician. Tom (wa8pyr) can run circles around me in his sleep! ...and I'm certain he has better toys!
...and "Mr. Lovell" reminds me of how old I have become. "Bill" sounds better.
Getting back on topic: The Summit and Stark "MAC" talkgroups are nice because they are assigned by someone, and Geauga does the same with their 8 TACS, but actually, the same thing can be accomplished using the 15 "LECOMS" in all MARCS radios (except for the assignment coordination part) for everyone on MARCS. (...ECOMMS for State Incidents) The MARCS folks were very foward thinking when designing the template involving interoperability.