There have only been two shipments imported; the first was part of a larger order distributed by Gravel and the second was a smaller one brought in by Questar. These have long since sold and there have been no subsequent shipments, hence why they're generally unavailable in Canada.
As for why they're also hard to find in the US right now, part of this is because Remington relocated manufacturing for the Bushmaster ACR last year - and this resulted in the supply dropping. They're also a more expensive rifle in the US, and I think a lot of dealers don't necessarily stock them because they're going to sit there longer in inventory.
The comments about being overpriced for their value are just BS: A high-end AR will run you about as much as a new ACR, so these type of comments general originate from either haters or people who would like one but just can't afford it.
And that's fine - there's always the XCR.