Given that there are only, what, two dozen transmitters left (if that), the cost of leaving them on overnight is probably negligible. It's probably cheaper to let them run & not worry about whether it's going to come back up at signon in the morning.
That, and if they're running the whole network from one site, there needs to be someone there all night anyway. If Vancouver's programming day ends at 1am PT... well, that's 5:30am in NL, time to bring up St. John's. Might as well run some reruns on everything in between. In any case, it's probably all on automation these days.