Just have to find a way to meet a medium. Perhaps make it to where if a dispatch is on then all 911 and radio transmissions would go to the dispatch. Now if the dispatch like Khub said went AFK or is not doing his/her job then it can be toggled to send a transmissions to the other officers.
I like the idea that all calls go to dispatch, its how it should be, and it gives dispatchers something to do. Granted dispatch my get a overhaul of calls if lets say there is max server and 10 cops, 3 Fire, 4 EMS online.
Not sure if there is a limit to the amount of dispatchers but if lets there max is 3, and there was a way to "Specialize" in a department. One dispatch would only receive transmissions of cops, other fire, and the other EMS, but they all receive the 911 calls. That way each has their own perspective areas and if they find a common place to be then they can easily organize all the government officials to respond to certain situations, (car accident requires a police for traffic control, EMS for injuries, and fire for putting the car out.)