So, maybe a SSM - Sudbury - North Bay - Toronto routing?
I do agree there should be some sort of business case for doing it. It should not just be done because "I want a train". If we were to look at the business model of the Northlander, and base it around that, it may stand an equal chance of success.
The only times I have ever flown int/out of Sudbury or North Bay was due to being required to for work.The cost of the flights are stupid high and if you can drive, it is not worth it. So, really, this idea would be competing with driving. If someone in T Bay is going to Winnipeg, most likely it is to shop.They likely are not flying if they plan to shop. I don't know if people go to Winnipeg for medical things, but I think for those, they fly to Toronto. While I would love a Winnipeg - T Bay - SSM - ... - Toronto route, I do not see a real use for it. The area between T Bay and SSM is too car dependent for the train to be a real success.
When it comes to the line's state, being able to do at least 40mph is needed to be worth using it for passenger service. Of course, I'd rather it higher, but as a minimum on the start day, 40mph is a must.