A coupe more data points.

Earlier I spoke about being awarded $1000 by the CTA. I had a friend on a separate itinerary travelling on the same flights that also ended up being awarded the same amount. The cases were submitted together but the process began for my friend after mine had already been completed. I found it interesting that I had provided my case information during the response step of my friend's CTA to have them refer to it but they mentioned in their response that they do not review previous cases due to their confidential nature. Rather, they evaluated the case separately, and despite having slightly different rationale (and slightly different information provided about the delay by AC), they still came to the same conclusion.

Recently had another delay YYZ-YAM that ended up being more than 3 hours. There was an initial 2.5 hour delay blamed on maintenance but I found via tracking that the FIN which was originally scheduled to operate my flight when it was listed as "on time" first flew to YXU, returned to YYZ and then operated my delayed flight. This was compounded by a required tire change once the aircraft returned from YXU so that the final delay was over 3 hours.
I anticipated that AC was going to decline my compensation request and I was going to have to bring it to CTA and then submit evidence that the most significant delay was caused by the aircraft was used for another flight before returning for mine. I believe that would be be considered operational/commercial rather than maintenance so would be eligible.
However, surprisingly AC approved the initial compensation request without any further action required. Full marks to AC for that one.