Just to clarify, as I understand it, one major motivation for the province to take over the TTC would be that, if it actually owned it, it could effectively amortize the costs of new construction over several years. If instead it just gives the money to the city to do the building, financial rules would require it realize those costs all in one year. In other words, it would make far more financial sense for the province to build its own subways than to pay to build someone else's. So the proposal for the province to take over the TTC was not just about "uploading" costs, but also about making subway expansion more financially feasible.
Perhaps someone here can shed more light on this issue.