I have seen and watched these two vehicles for a few years now. They are from Harris RF Communication Corporation. Harris makes radios for the military, police and others. I suspect these are test vehicles and as they drive all over town they are testing product reception and other issues. A few times I have seen a person standing outside the vehicle with what appears to be "rather large" walkie talkie.
Maybe one of these days I'll get bold enough to approach them and find out what they are doing.