I hate to say it but 4G for an emergency network is just a money sink. I hate to have a defeatist attitude but at least in my small new england town this would be a complete waste of time and money and effort. We have no unified dispatch system. All land line 911 calls go to police. If you want Fire or Ambulance it's transferred to the Fire department, who then transfers medical calls to the ambulance. If you call from a cell phone it goes to the state police regional office first, then to the local state police barracks, then to town police, etc. Police and fire are on separate frequencies. ICS is a joke and never implemented. EMA is run with all donated equipment and goodwill of Ham operators. Better than nothing? certainly but not by much. I put an IP camera onto their EMA vehicle, punched a hole in their firewall and the chiefs were able to view the scene and control the camera from the EOC. It took me 10 minutes but it was like the natives seeing an airplane. The average Police/fire/EMA chief is 50+ years old and typically holds a grease pencil, not an iPad.
Example, there was a mill fire in the neighboring city. Multiple towns responded. No ICS, no communication plan, everyone on one channel walking all over each other. There is no way any of these communities could implement, monitor or effectively use a 4G solution.