Thick mount NMO's.
As for the Browning, probably some shop contracted to do the install saw a way to save a few bucks and pass on the heartache to the next tech down the road.
Probably sufficient ground plane when you look at the antennas:
Far left looks like a cheap 700/800MHz antenna, would only need 3" of metal in radius under the antenna to be good. Doesn't look like 3" to me.
Center is either capped for future use, or a GPS antenna.
Far right looks like a 5/8th's wave UHF, would want 6" radius of ground plane under the antenna. Even says "UHF 450" on the whip. Not enough ground plane. Might be a 1/2 wave, but can't tell. That wouldn't -require- a ground plane, but providing an offset one like that makes the antenna a bit directional.
Kind of perplexing to see an install like that for a state agency. Nice headache rack, but the antenna installation leaves something to be desired from my (internet) point of view.
Usually a standard headache rack doesn't supply enough ground plane to be useful. The large plate on there holding the light bar is helpful, but looks like a compromise.