They use both. All traffic is aired on the VHF though whereas only some transmissions are on 800. The reason being is because Guardian ambulance doesn't have 800mhz radios in their rigs.
Do you no longer receive Ponderosa Fire District? I used to be able to listen to their radio traffic on the Flagstaff Fire and EMS feed to hear the specifics for calls I received via CAD page. I have not heard them at all for approximately the last three weeks.