Living in BC -- but not towing my R-25 -- I thought I would troll through the BC Regulations and see if I could give you any information. What a waste of time! I can't find any information on the web for you.
If you are planning on cruising the Pacific Northwest (now known as the "Salish Sea") you should put your boat in the water in the US and save yourself a lot of problems. Crossing the border by boat is easy (ship documents and passports, of course, and no firearms!) and I think there are better storage facilities for your truck and trailer in Washington State rather than BC.
Of course, if you plan on cruising lakes in the interior, this isn't a good recommendation.
Also, don't assume that Ontario permits are good for BC. Our provinces don't play well with each other in a lot of things.
Dave
"Lobo"