Anything with an out of country origin will have GST applied by the CBSA based entirely on the bill of sale. That is what we have termed 'duty' and run to the boarder shops for 'duty free' smokes and shit.
I worked in a postal outlet and had many crazy experiences with parcels of all sorts. A guy sending knives and throwing stars to Australia actually got them back!
From time to time, a regular customer would recieve a parcel with no customs fee from a supplier outside the country. This was random at best, maybe karma. Anyway now that you have brought this sight to my attention I'll check it out.