I've crossed the border between the US and Canada many times via Train,Plane and Automobiles( didn't see Steve Martin or John Candy) and have never had any problems with the Canadian officials going into Canada!
The story is different with the American ***** upon returning however! For some reason the ones that work the border crossings where vehicle and train passengers are checked, especially on buses, have been the rudest and least friendly of any I have encountered anywhere in the world, and that's saying something!
Of note: back in the day when the draft was still in effect and the Vietnam mess was in fill bloom, young people were checked to see if they were registered for the draft; if not they were arrested by the guys in the back with the flat tops and big necks!
Canada, on the other hand, welcomed draft resisters and dodgers and many
never came back until President Carter pardoned them during his term!
The stop @ the border to collect the
customs declarations is government @ it's worst, the train doesn't stop anywhere in Canada, so what's the point?