Well here's your answer from one of the members of the Montreal Airport's board (a non official discussion forum)
This flight was not diverted to YMX but rather to YUL last night, at about 10pm. The reason is because the plane (an Airbus A-330 C-GGTS) had lost its hydraulics and capability to make turns while in the air ( ! ).
He made an emergency landing on runway 24R and all the firetrucks were there because they were concerned that the plane would skid off the runway but it managed to stay right on track. It made a complete stop on the runway and then all the trucks went to the plane to make sure all was allright. It was then towed to gate 33 where all the passengers were later transferred onto PTV's.
They need to make major repairs on the plane before it leaves again. Last time I checked they were supposed to leave YUL at about 3h45pm today sunday.
Looks like your cousin might have quite a story to tell.. hope she arrives over there safely. The plane should leave in about 3 hours from the time I'm posting this.
[Edited 2005-08-07 19:10:10]