Yes this has happened at AC but only when flights are full and there are last minute schedule changes. Usually the employess and/or guests just get left at the gate without having to get on.

I was on an AC flight from YYC-YVR this spring. We were all on board while they tried to fix a mechanical. About 40 min after our sched dep the pilot announced we'd still be a while trying to get things fixed. I needed to be at work in a couple hours so I got off and got a seat on the next flight leaving in 15mins(tango fare and got myself an exit seat.) Got on the next flight and shortly after I sat down they paged the dead heading Zip crew to get off as they now had a flight to operate. A few more people from my original flight got on and we were on our way a few minutes late.

The Zip flight then took 117 people from the mechanical flight to YVR.

It's a good thing the Zip crew took up the overhead space with there luggage or we could have been several more minutes trying to locate things from underneath.