AC should have taken the opportunity to pay the same rates that the subsidized carrier was paying.
If YEG can afford to subsidize new airlines it should be able to offer the same rates to existing Airlines.
I would have remitted the same landing fees as the upstart rather than what the airport was charging AC. Then let the Airport authority justify the different rates in court.
It would never get passed the discovery stage as someone would get fired as soon as the finger pointing started.