Agree that avoiding the PST in any province but Alberta is unlikely, registered or licenced. Duty does apply to boats built outside NA, however in our case we were able to get the duty portion reduced by itemizing and valuing NA accessories and upgrades during the boat's time in the US. (eg, cabin heater, new gearbox, recent sails, new stove, etc etc.) We successfully reduced the duty portion by approx 30 - 40% of the purchase price. We had letterhead documentation on this from the selling broker.
Given the recent rise of the CDN dollar vs USD, importing makes more sense than ever, in many cases even if duties (and trucking) are involved. The selection is much better.