It is my limited understanding that Questar is the only one so far that has submitted the mag design to the RCMP for approval. Everyone else in Canada who is selling the 10 rounders, is selling what Questar imports from their manufacturer stateside.
If anyone else wanted to make a legal AR pistol 10 rd. mag, they would have to follow the same process of submitting prototypes to the RCMP for approval.
I think it was great of Questar to try this, and to go through the headaches of getting approvals and opening this product line. Support innovators like this, and buy Questar!