About a year and a half ago, I arrived at YEG for a flight to YOW via YYZ. My YEG-YYZ flight was delayed (and would have resulted in a misconnect at YYZ), so they put me on an 'extra section' YEG-YYZ - leaving about ten minutes after I got to the airport - which was filled with passengers whose original YEG-YYZ flight had been delayed (mech.) about eight hours.

IIRC, they served a free drink to everyone onboard and apologised a number of times. Upon arrival in YYZ (after a go-around, of all things!), two agents were at the top of the jetbridge handing out a letter of apology to all the passengers, who could fax/send it in to have 8000-9000 Aeroplan miles credited to their account.

It seemed quite well-handled, but I did hear a few passengers grumbling that AC didn't provide a meal voucher while they were waiting in YEG. While that maybe wasn't required, it probably would have gone a long way to making those passengers, delayed eight hours, feel appreciated and cared for.