I've helped someone through this process before - in their case it was a plane that developed a pressure leak over the Atlantic and had to turn back. AC provided overnight accommodations for the passengers etc... but denied the 600EUR claim.

After filing with the Irish aviation authority, Air Canada responded with an extensive set of documentation to demonstrate that the plane was well-maintained and the delay could not have been foreseen (i.e., these filings get treated seriously by AC). The authority concurred and claim was denied.

Expect a few months wait and a high likelihood that AC will provide sufficient evidence to justify extraordinary reasons for the delay and therefore no payout. Anything you overheard from gate staff is entirely irrelevant, unfortunately. That said, nothing wrong with trying.

As for your small claims court, suspect that AC acted within the conditions of tariff and therefore no damages apply - but then IANAL.