When I built mine years ago, I researched this quite a bit. I formed the opinion then that these are not at all legal to simply hop on and ride. Occasionally I would sneak a ride through town or around my neighbourhood always trying to lie low. Then I started seeing other people riding them around so I got a little braver and now regularly drive by cops at a leisurely 30 - 40 km/h and seem to attract no wrath.
I believe that this is a classic case of RCMP exercising their discretion and, unless something has changed, they simply are not going to bother ticketing riders for driving unlicensed motor vehicles which are providing cheap transportation and fun in a relatively harmless manner.
As these machines proliferate, and as soon as there is an incident such as someone ripping down a sidewalk with no helmet and thongs and running down a mom with a baby in a stroller, then there will be enforcement.
I always wear a helmet (sometimes just a bicycle helmet), I've kept the muffler restricted, and I seldom go over 30 km/h. So far so good. It would be a shame if this little infringement against the Motor Vehicle Act started resulting in prosecutions. I could see this happening if riders believed they could ride these machines in a reckless and offensive manner. The bad guys always spoil the fun.
Peace & Grease, Dennis