Canada's Toronto–Quebec City high-speed rail programme could cost as much as CA$113 billion to build, according to a new estimate from the parliamentary budget watchdog, which also found the project would deliver only a modest short-term boost to the economy.

The figure sets a new upper bound for one of the largest infrastructure commitments Ottawa has made in decades. The corridor between Toronto, Ottawa, Montreal and Quebec City carries a significant share of Canada's intercity passenger traffic, and the proposed high-speed line has been promoted as a way to cut journey times and shift travellers from air and road to rail.

What does the watchdog's estimate change?

The watchdog's role is to provide independent costing of government programmes, and its assessment now anchors the fiscal debate around the project. The CA$113 billion ceiling gives parliamentarians and taxpayers a concrete number against which to test the government's own budgeting.

The accompanying finding on stimulus is less favourable for advocates of the scheme. According to the watchdog, the short-run economic stimulus the line would generate is modest. Large capital projects of this type typically spread spending over many years, meaning the immediate impact on output and employment is smaller than the headline cost suggests.

How does the cost compare with the expected benefit?

The watchdog's analysis separates two things that supporters of the project often combine: the long-term case for faster rail in the corridor, and the near-term macroeconomic return on the construction spend. On the second measure, the report's verdict is restrained.

Proponents of high-speed rail in the Toronto–Quebec City corridor have argued the line would reduce congestion on parallel road and air routes, lower emissions, and support denser economic activity along the route. The watchdog's short-term stimulus finding does not test those longer-run claims directly, but it does complicate the argument that the project can be justified as an immediate job-creation measure.

The CA$113 billion figure is an upper estimate. Final costs will depend on alignment choices, station locations, electrification strategy, and the pace of construction — all of which remain subject to planning and procurement decisions that Ottawa has yet to finalise.

What happens next?

The government must now weigh the watchdog's costing against the project's stated long-term benefits as it moves through planning stages. Future updates to the cost estimate, and any formal response from the transport ministry, will determine whether the CA$113 billion ceiling holds or shifts as engineering work advances.