That's exactly what we're talking about, and its a perfectly sensible idea.
It wouldn't require hundreds of billions to nationalize some corridor, that would buy you both freight carriers lock, stock and barrel.
Where do you get this stuff from? There are no 'special' laws protecting railways from nationalization in whole or in part.
Canada doesn't not have constitutional property rights in any event, which means that any rights that did exist in law could be repealed.
But for the record, no one is suggesting 'seizure' of the rails.
The government has plenty of means at its disposal, both carrot and stick to garner cooperation.