In my experience, Toronto's subway just stops when there is a power outage. I did a bit of poking around and power is supposed to come from two independent substations so that power can be switched over. There is battery backup, but it isn't for traction. In case of longer term outage at a station, generators can be brought onsite. But again, these generators aren't intended to supply traction power. The New York subways system operates under different rules and different expectations, running 24 hours a day. And it operates tunnels under water. Not only does the Toronto subway shut down every night but periodically it partly shuts down on a weekend for maintenance or upgrades. The risk here is that because of the opposition to shutting down for maintenance, the maintenance and upgrades take years and years longer than they would elsewhere.