Westjet transitioned to the new reno'd A pier in June. The rear exit/entry gates are A1, A2, and A3. WS also has gate A4 and A5 that are conventional.

FYI, even if your aircraft arrives at one of the special gates, the company doesn't use the rear exit all the time. On my recent flight (full aircraft) the whole airplane had exited through the front door before the rear door was properly positioned. The aircraft beside us at A1 was departing for CUN and the boarding process did seem a little faster using two doors.

The only rear loading bridge WS paid for was the the prototype in YYC (gate D40), these bridges are paid for by the YVRAA with your $10-$15 AIF.