On my side of the border there is plenty of places to camp trackside. My favorite is at Basque, BC, just south of Ashcroft. The CN/CP shared traffic from Mission ends here and there is a crossover for the directional running. Lots of open space near the tracks. You will be on someone's property so be aware to take only photos and leave only footprints.

I did find an old Canadian National Railways soup bowl half buried there. Another thing that I found up in that desolate area was a Budweiser beer can that was commemerating Superbowl VI! It was half faded but still okay on the one side that was facing down.

almo