Connection situation at YYZ is very bad these days. They keep passengers on the airplane sometimes for more than 2.5 hours until the main immigration hall get less crowded.

It happened to me last month when I flew from LHR to ORD via YYZ. They kept us in the airplane for long time almost 3 hours that I missed my connection to ORD and had to spend an overnight in the nearby airport hotels and payed for the cost of accommodation by myself.