The Polar Bear Express is definitely an experience. It was generally very sociable, as you say, and it would stop pretty well anywhere along the tracks if flagged down. Some people lived in extremely remote locations along the general vicinity of the tracks.
One story - my ex was asked one day to go in the medical helicopter to pick up a laboring woman whose husband had brought her from bush camp to a spot by the tracks and radioed for help. The helicopter pilot elected to land on a long high trestle bridge, in the center of the long span, because the bush was so dense everywhere else. They landed, shut down, and started walking toward the woman's husband at the end of the railway bridge, when the man began waving his arms and screaming. The train was coming.
There wasn't time for them to make it to the end of the bridge; they sprinted back to the helicopter, got it started, and pulled off the bridge JUST as the Polar Bear Express came through.
They did pick up the woman after that and she made it to the hospital on Moose Factory Island before delivering.
And polar bears ... they ARE the baddest bears. Not only are they the biggest; they fear nothing, and they won't just kill you if you surprise them or invade their territory, they will actively hunt you. Have you seen the documentaries on polar bears in Manitoba, where they take people to look at them in enormous tank-like CAT machines? You need a machine like that. The local people in Moosonee hunted just about everything but they stayed far away when the polar bears came around.
I have a phobia of bears and took my brother-in-law's shotgun to Moosonee with me. What an idiot! A bear would've regarded that shot as no more than black flies biting.
Fortunately we were never visited by any bears. They didn't come right into town the year we were there.