Two things that Europeans often don't get about Canada:
- It's big. Really big. Toronto to Vancouver is 2000 miles by air, 2500 miles driving (you can't go straight, there are Great Lakes and mountain ranges and such in the way)
- Our trains, by European standards, are few and far between. Little villages in Europe have three trains a day between them, but this flagship run - Train 1! - why, the very symbol of our nationhood is that "last spike" image and the ribbon of rail from sea to sea "there was a time in this great land" etc - runs only three days a week. And it takes 4 days to get there. See point 1.
So if you don't mind waiting a day (or 2 or 3) in Toronto to sync up schedules with the train, and then taking 4 days to get there, it could work. Which brings us to the third problem with the train system in Canada:
- It's expensive. $600+ per person for the months-in-advance-no-changes-no-refunds tickets to sit in a seat (no bed, and it doesn't recline much) with blankets and pillows available for purchase. $2500 each to share a "cabin for 2".
Now I won't deny this is a beautiful country. And seeing it from a train is one of my favourite things to do. I use the train between Toronto and Montreal and far prefer it to flying between those cities. But I've used trains in Europe and it's important for a tourist to know what "train" means here - they are not the same.
If they still want to do it, going into it with their eyes open, then open jaw plane ticket is the way to go.