Rural/Metro in Central Indiana is 155.235 MHz, DPL 412, callsign
KRR913. It is simplex from base to truck, however some trucks have mobile repeaters in them that cross-band from VHF to UHF for the portables they carry, and vice-versa so they can use their higher-powered VHF mobile remotely from their UHF portable when out of the truck. This is like the mobile extenders ISP used to have back when they were on VHF low-band.
Generally, the mobile repeaters are low-powered on the UHF side, and they have varying frequencies and PL/DPL, none of which I know offhand. Also, when monitoring on a scanner with a back-of-set antenna, you will usually not hear the mobiles unless they are within a few miles of your location.