I'm not going to bag on the owner's choice of tug. For all I know s/he bought the MP3 hoping it would be more stable, found it not to be the case, then bolted on the car.
The 2-4 wheel MC/Car thing goes by jurisdiction. I'll bet the rider gets a pass unless the law really wants a reason to hassle somebody.
The MP3 actually handles very well. The front wheels lean parallel to eachother at speed and can be locked upright at a stop. If locked upright they unlock at a pre-set speed. So if you want, you can putt feet up through busy city traffic then ride like a MC when you get up to speed. Then, when time comes to stop quickly you have twice the grip of a standard cycle due to two braked wheels up front.
That won't keep you from crashing, though, a colleague layed one down during a test of the parking brake when he (a shorter guy) overestimated the length of his legs and underestimated the slope of the test hill!
That said, if the rider of this rig set his lean out when unlocked, then locked in, it might cause a lot of strain on the mechanism and some bad handling!