On that particular weekend, MT had some issues generated by at least one tech aircraft (A330?). The techical fault required approx 36 hours to repair (nosewheel?) and this resulted in a number of flights being subbed out to other operators. This, in turn, is why I found myself sitting in YYZ Hotac for 13 hours rather than "resting" on the sofa on days off.
I can't say for sure that this is why your aircraft was changed, but it seems highly likely. This kind of tech issue affects all airlines from time to time: Nobody is immune. It's bad luck, but at least you are home now
