I don't know about those counties, but m vehicle has 2 round black antennas like you describe, they are for the 800mhz radios in my vehicle. Just a different form of a whipless antenna. If I remember right, they are marketed more towards transit, like busses and such. So that would be my guess. I have seen GPS/MDT antennas look like that too.
I think maybe one GPS & the other for MDC? There is also quite often a black cylinder-shaped antenna, about one to one-and-a-half inches tall, which is for the MPSCS radio. I've noticed a lot of county & city cars sporting these lately, too.