Completely a political rather than a technical question. Watch your local media, city and county commission meeting minutes. If a change like that is coming, those groups will be discussing it.
Unfortunately, this is all so true. But for the OP, if dispatching is carried out from more than one jurisdiction (say FD and PD in this case) in the same dispatch center, yes there can be multiple bands and/or technologies utilized by each individual department. It all depends on the radio consoles, each having to be compatible and programmed to the system in use. OR, with advanced enough console ability and design, be able to switch each console.
Here where I am, police use a UHF P25 system, while fire and EMS use VHF high analog. Everything sits in the same big room, but there are 2 'sides', the police side and fire/EMS side. Same room, different sides, different bands and technology's. And our system is big and busy enough to have separate PD and FD dispatcher, only a few of which are trained to do either side. The rest it's one side or the other.
Here and all over the USA, new systems are bought by the local government, and placed into service with little to NO input from the people using them; not during the initial looking at phase, design, etc. These systems are put put in place, and the turned over to the responders that use/depend on them.
And many times, there are problems once these new systems go hot. Now with millions of dollars invested in these system, they are strapped with them. Sometimes they just need a little 'tweaking', maybe need additional repeater sites put in, or, worst case scenario - have to scrape the new system all together and go to something different, or back to their old system.
The RR database is the best place for system information. Media coverage on the new systems going in sometimes very short on information; sometimes it is never covered at all.
So, it is pretty much a wait and see situation. If you know any police or firefighters in the area involved, ask them. But even with this, they often have little to no information about what is going on, until they actually have it handed over to them.