WestJet doesn't own any of the gates on the "D" Pier which can be used for inbound international flights - meaning, those gates with the passages to Canada Customs; gates 42, 43 and 44. All of those gates are owned by the Calgary Airport Authority.
The widening of the "D" concourse was held up because of funding problems (rumoured to be because AC
was not paying its rent to the CAA, to the tune of a few $M).... but in any case, the "D" concourse is progressing steadily. Those gates are rumoured to be slated for transborder use; however, the prior owner of the gates on the "D" concourse was AC
.... they inherited those gates from Canadian Airlines.
As for YYC
service to DEN
.... well, it looks like AC
already have that market sewn up out of YYC
- they do at least a 2x daily between the two cities.