Both. I think it lends just enough plausible deniability if they did get stopped by police, but provides a certain amount of cover by creating some hesitation t

Both. I think it lends just enough plausible deniability if they did get stopped by police, but provides a certain amount of cover by creating some hesitation to identify it as either a private vehicle or a cop car (i.e., creating uncertainty) and prevent stoppage and other slowdowns. A friend of mine used to drive a Ford Crown Vic with a whip antenna on the rear that was actually an unmarked ex-cop car. When he would get in the passing lane, he'd never get blocked—US drivers recognize white or dark blue Ford Crown Vics and Taurus models as common police vehicles and usually change to the right (non-passing) lane immediately.