The federal government will kick in more than $1.8-billion for ‎Ontario's plan to improve GO Transit, freeing up provincial money for other transit projects.

Prime Minister Justin Trudeau came to a GO rail maintenance yard in the west end of Toronto to make the announcement, calling it a contribution to "the single largest transit project" Ottawa has invested in.

"These funds will help improve the lives of millions of Ontarians," Mr. Trudeau told a crowd that included railway workers, federal politicians and several regional mayors. "The GO network will mean a faster commute, less time in traffic and more money in people's pockets, as they trade their cars for public transit."

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The province has been working to turn GO Transit from primarily a commuter service into transit offering two-way service throughout the day. Dubbed Regional Express Rail [RER], the plan involves switching from diesel to electric trains, adding stations and boosting service frequency.

"All three levels of government are now working together to deliver GO regional express rail," said Premier Kathleen Wynne, a reference to the latest iteration of Toronto Mayor John Tory's election transit promise dubbed Smart Track, which now involves the city paying to build six local stations on existing GO lines.

"[Requests for quotation] have been issued and shovels are going into the ground. The work is being done. Stations are being upgraded, new track is being laid and new rail crossings are being done."

The project is by far the biggest-ticket item in the provincial transportation plans. It has a multi-year horizon, though, and Progressive Conservative Leader Patrick Brown has not signalled whether his poll-leading party would continue with the plan if it wins the 2018 provincial election. It has been tentatively budgeted at $13.5-billion, which Ms. Wynne's government had pledged to fund.

‎The federal money will not change the scope of RER but will free up some of the funds the province has allocated to the idea. Ms. Wynne said this would allow the province to invest more in "the other priority transit projects throughout the region."

Ontario Transportation Minister Steven Del Duca said it's too early to know whether the money will remain dedicated to regional transit or whether it could be available to local projects.

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"To that specific question, I would say we haven't necessarily landed just yet," he said. "I have no doubt we'll be able to find a way to dedicate this capacity to projects, whether they're regional, whether they're more localized in nature, because we know the demands, for the time being outstrip the resources."

Ottawa promised in the recent budget to spend about $20-billion on transit over 11 years. The federal contribution announced Friday is leftover money from the New Building Canada Fund, set up by the previous federal government, and will not count as part of this total.