Portland, OR takes some hard stances on prostitution. While there in 1998, I was told that undercover officers there pose as SW and if they catch you on solicitation they take your car.
There is the age issue, unfortunately the law gets pretty black and white. But even if the guy was innocently driving, sometimes a couple years in lock up might aide the stupid.
They used female cops undercover as SWs on the street, and if they got the magic offer, they'd confiscate the John's car. So if a cabbie was a John I guess they'd take the taxi.