NORAD watches the whole sky and tracks everything coming close and entering North American Air Space. So they would definitely know about incoming Russian aircraft.
http://en.wikipedia.org/wiki/North_Warning_System
I'm surprised about deployment time though. When you figure out a Russian aircraft is on a North American heading, you have to scramble fighters from cold lake to the Arctic? Seems like too far of a distance to travel to intercept before they enter our air space. I would think it is much more likely that US Aircraft from Alaska intercepted the Russian bomber rather than Canadian Aircraft from Cold lake.