kEiThZ
Superstar
The terms for receiving federal funding spell out in great detail what they will and will not cover and what all the other parties have for obligations. I don't know how much leeway we would have since the Building Canada Fund request was approved. I would expect the province would be required to submit an official request for the change (on our behalf, since BCF is with the provinces) and any negotiations of who covers what would likely need to start from scratch.
Don't know for sure of course. You would need a copy of the current agreement to find out. Often it seems the municipality receiving the funds isn't told all of the rules to acquiring the funds, so we have no way of knowing.
Of course, this is all in the name of a transparent and accountable federal government which probably costs billions in paperwork and construction delays per year.
Working in procurement within the federal government, I can assure you that any agreement is negotiable even after it's signed. There just has to be the right political backing behind it. Ottawa dumped it's LRT plan after the feds pledged money. They recently pledged even more than the initial amount for an even more expensive plan that Ottawa's working on. If Toronto has the political clout, it can be done.