My reading of it is not that provincial legislation in and of itself would apply on reserve, because there would not be jurisdiction for that. Rather, the suggestion has been that the provincial law could be incorporated by reference, on an interim basis, pending a first nation addressing the issue.
That is one of the solutions. It's not the one I particularly favour, but my understanding is that there is a way it can be made to work legally. It's not unusual. There are some other areas of jurisdiction, including industrial development on reserve lands, where a first nation community not wishing to reinvent the wheel is adopting provincial laws by reference, and even provincial administrative regimes. It's not without precedent to go down that road, and it could be quite workable. But again, that's not my recommendation or preference, it's simply one of the alternatives.