AC applied for one of the four available-to-any-airline perimeter exemption slots to fly to YVR in the last round of new slots. Unsurprisingly, they didn't get it (AS-PDX, VX-SFO, B6-SJU, and WN-AUS got them that round), since YVR doesn't have a strong advocate in Congress. AA, UA, and DL each have at least one free beyond-perimeter slot that they could use for YVR if they wanted to, but it seems unlikely to me that YVR would move to the top of the list for a US airline unless there were many more beyond-perimeter slots.