I took the train up and bus back with the private tour company so needed my passport. We just held the passport up in the air and the Canadian Custom/Immigration agent walked down the aisle. He just looked to might sure everyone had a passport. As he passed me, he said “Welcome home” as I am Canadian.
If I remember when it was the roundtrip train ride, when we got to the end on the one way, we flipped the seats over to face the other way and were asked to switched to the other side. The train used the same track.