As for Amtrak being 'allowed' to carry within Canada.....the railroads never had the type of traffic restrictions that airlines and buslines had, as railroads usually had their own route, and could carry anywhere along it without any traffic restrictions....
Back in 1974 when the Empire State Express started running through Canada, the Transport Commission refused to allow Amtrak to carry passengers wholly in Canada. The trains would then have become eligible for loses under a funding formula the Government had with the passenger railways (VIA did not exist then) But after pressure from the local MP’s who’s ridings the trains passed through, the Government relented and Amtrak started stopping along the Canada Southern.
This is similar to what happened to the Penn Central 'Ghost' passenger trains on the same route across southern Ontario in the last few months leading up to Amtrak.
Penn Central had applied to the ICC and Canadian Transport Commission to discontinue the trains. The ICC refused but the CTC allowed the discontinuance so Penn Central just ran them non-stop across Canada other than for Customs and crew changes.