Having been in the fire service for over 35 years myself, maybe I do understand some of the problems that come up while fighting fires. Also having worked for a couple of engineering and consulting firms along the way, I have been out in the field working with both public safety and federal agencies that have requested help in molding their communication systems into something better. I travel the country frequently going to dispatch centers to work on radio interoperability systems. There isn't much that I haven't seen or heard about system problems on these trips.
What I have read here and try to read between the lines here doesn't provide enough information to even draw any conclusions. Let us try to keep the bias out of out opinions and stick to the facts that are lacking in the presentation so far. If you have the start of a UHF system, then continue to build on it. If it doesn't provide the total coverage the county needs, then improve on it. But don't throw it all away and start over on a new band. Unless your in a city environment, stay away from 700 or 800 MHz. It will take way too many sites to provide good coverage. Unless you have a bunch of VHF channels, it makes no sense to migrate to that band. So your stuck with the UHF. Like it or lump it, it is the best bet.
With all that said, I don't give a rats butt about the politics on this system. Find a way to settle the problems and move on. Don't let some wild man at the top steer the game here because some company comes in and lays some grand plan in front of you. Make them show you how it will solve the county problems and not fill the bank account of the radio company. Make the company produce coverage plots, tower locations, real costs of building towers and shelters, provide generators and a good grounding system. Depending on how far apart the sites are and the type of countryside, is a microwave practical or running fiber underground a better selection. Don't rely on telco lines to connect your sites back to the dispatch center.
Facts and numbers people. You can't make decisions without the facts. Then get someone outside the county with no interest to go over the findings to make sure your going in the right direction.