614 has scheduled departure time 1435. If you were there at 1416, I would submit an IDB claim to AC, then when they refuse to pay, to the CTA.

You just need to be very specific in your wording. You had a confirmed reservation for 614, including a boarding pass (meaning you made the check-in cutoff). You were at the gate 19 minutes before departure (is it cynical that in these situations, I would take a photo of the gate board, with time?). You were denied boarding, and told that other people were in your seats.

Short, sweet, and covers all the bases. Just make sure you read https://www.aircanada.com/content/da..._tariff_en.pdf Rule 90, and explicitly make it clear that you met the check-in/boarding deadlines, etc.

It looks like you were delayed to YHZ by 2-6 hours, which would mean a payment of a $400 cheque, per person.

These "auto rebookings" come up way too often, and they're unacceptable.