I paid more attention for my YYC–YVR flight today, and won at YBYL!

Business class showed as 14/14 booked at check-in and I was second on the upgrade list when boarding started. It suddenly dropped to 11/14 while I was in line for zone 2 boarding, so I stepped out and asked the agent at the counter. In the end, I got an upgrade along with one other passenger and an AC crew member in uniform. The others (including whoever was first on the list) on the upgrade list dropped off as they presumably boarded.