It's baaaack...

[GSPI]

So it's an SSP but possibly for the Clayton County Police?

I wonder as Clayton County does have a group called H.E.A.T. which is an initiative by the state amongst various departments for an aggressive driving traffic enforcement unit. These cars are all low profile variously colored dark cars. Might be possible to check with them about this:

http://www.claytonpolice.com/TrafficUnit.htm