That´s interesting indeed. Your annual or biennial vehicle safety- and emission inspections must be pretty easy and relaxed then. But on the other hand you need extra turn signals mounted on the handle bar of some scooters, because the built in ones are not good enough...
Not so here in Europe. Here the tires must fit the proper tire size/dimension given by the vehicles manufacturer. Therefore the built in turn signals are way good enough. 
And not only this, most advocates highly recommend to use only tire brands/models which have explicit clearance from the tire manufacturer or the vehicle manufacturer for the specific bike model. Just to avoid insurance issues in case of an accident and not leaving doors wide open for "hedge lawyers".
But like an old saying: "No risk, no fun!" 
It's a different world over here. I have been riding for over 35 years and have NEVER had to have any of my bikes inspected except to verify the VIN. Some states require it but not any of the states I have registered a motorcycle or scooter in.
As for running car tires on bikes, it's not that uncommon here. I have ridden with a number of riders running CTs. Safety does not seem to be an issue. The only real "issue" seems to be a different feel than with MC/Scooter tires.
Legal issue? I have seen that brought up in forum discussions as a reason not to run a CT but have NEVER seen an example of anyone running into legal issues from running a CT.
Like I mentioned it's a different world here and you will see some strange stuff. These look like tractor tires:
It's even possible to register home made contraptions like this:
