Normal shoulder mounted crossbows are legal in Canada, no form of PAL is required to buy one. They are not controlled at this time as are firearms. The one form of crossbow that is prohibited / restricted is the small, one hand version, normally about the size of a Handgun. Each Province has their own restrictions in regards to hunting. As an example, in Alberta you may use one during the normal firearms seasons and during primitive weapon seasons. They may be used during the archery seasons, but only if you have a medical certificate from a physician stating that you are not capable of using normal archery equipment, and only then if you obtain a permit from Fish and Wildlife allowing you to use it during the archery season. There are some very good ones on the market, Bowtech, an archery company produces one that exceeds 400 FPS.
PSE, another archery company produces one that actually mounts on an AR15 stock which is utilized by the U.S. military, and they are achieving 4 inch groups at 100 yards.
Most credible archery stores can give you an abundance of information.