I disagree Lily. I'm not sure where you are but in Ontario when you present a status card your PST is removed, not payed for. As far as delivery, yes, items do have to be delivered on the territory to receive the PST exemption. In stores though, at least in Southern Ontario, i don't know about everywhere, you are PST exempt at the point of sale if you present a status card.
Beyond that I do absolutely believe that Native people, on territory or off, should be PST exempt.