The smoke wasn’t coming from the tailpipe. Seemed to be coming from under the car near the front.
As I pointed out to the esteemed doorhinge. With no great success. 
I can tell you from experience that ATF dripping onto a hot exhaust makes for a lovely smoke-screen.
Has an unmistakable horrid smell too, brake fluid is awful too, real eye burner
Or the driver was rolling-dirty and blew a huge disgusting cloud from his E-cig out the window.
(Internally, its probably a similar process.)