UHF antennas
They could be part of the video system. If there's a dashcam, there's most likely another antenna for it.
One antenna for the wireless mike, and another to feed cached video back to a server when the car is close to a station. Just a possibility. Is there just one or two vehicles in your area with these UHF antennas?
In my area, video is done on VHF, although everything else is trunked 800.