Originally Posted by
noobynoob
How does this work for connecting passengers?
Do I need to transfer from concourse D to B as if I were making a domestic connection (pass through immigration, etc.) and then trek back from B to D?
It depends.
At the moment, YYC has all concourses (except the core of the US pre-clearance Concourse E) open as one secure area. That means that they can't facilitate sterile international connections and, thus, you'll have to enter Canada in order to board the London flight. Once you've entered Canada you can go anywhere in A-D, so getting to the Lounge in B is possible.
If YYC were to go back to a sterile connection model you'd be stuck in Concourse D, unless you entered Canada. WestJet provides access to the Aspire Lounge in Concourse D, if travelling in Business or based on status, so you'd still have access to a lounge.