When my dad brought his across he talked to a local wrecker who continually imports restored and modified vehicles, as well as late-model vehicles into Canada. They told him the same rules, but as was stated in what you posted, "Importer must be able to provide proof that the vehicle is fifteen (15) years old or older as determined by the month and year of manufacture".
They clearly said that this applies only to the vehicle. This was also echoed by the customs officials he talked to before he even went down to get the vehicle. They don't care what it is, they just want to make sure all the paperwork is in order when the car comes through, and that it is what you say it is. If you get one that wants to argue differently, it shouldn't be too hard to talk to a supervisor or higher-up and get it cleared up.
These cars come across every day, just make sure you have all your paperwork in order.
My dad is a mechanic who also does out-of-province inspections and makes sure things are done right per the law. If there was a chance they wouldn't have let it in, he wouldn't have taken it. He did all his homework and made sure it was legal to bring it back and everything was done correctly. He even made 2 trips to get the car because the first time the car was titled by the frame serial number which was covered with the new engine mounts, so the previous owner had to get a new title made with the body serial number before they would risk bringing it across.
