It may be different province by province. If I am buying used here in British Columbia, I don't have to pay the 5% federal sales tax (called the GST - goods and services tax). When I register the vehicle, I do have to pay the 7% provincial sales tax (PST, although officially it is called the Social Services tax). If you can get a temporary plate from your state, you won't be paying any taxes in BC.
If you are considering an buying a new Escape
here in BC, their web site says:
There are no taxes or duties payable on the purchase of an Escape Trailer. When you arrive to take possesion of your new Escape, we will provide you with all the necessary forms required by the border to import the trailer into the US. When crossing into the the US, a confirmation of the VIN is all that is necessary and you are on your way.
I know that there is no provincial sales tax in Alberta. I know that the GST and PST are combined into one tax called the HST (Harmonised Sales Tax) in many eastern provinces.
If you are from California, I direct your attention to this thread