High-speed rail line could see long tunnels beneath Montreal, Toronto, raising costs

Alto, also known as the Toronto–Quebec City High-Speed Rail Network. (photo: Alto)

A planned high-speed rail line between Toronto and Quebec City will include tunnels in Montreal and possibly Toronto, says the Crown corporation overseeing the undertaking, whose budget some experts warn may be stretched as a result.

In an update on its website, Alto says it plans to burrow from just north of the river that rims Montreal’s north side to downtown in a north-south corridor that would exceed 10 kilometres.

“To reach Montreal, the current hypothesis involves building a tunnel under the Rivière des Prairies and Mount Royal to access downtown directly, reducing integration challenges in a dense urban setting,” states Alto’s preamble to an online survey about the proposed railroad.

It is also considering tunnels or elevated tracks to reach downtown Toronto “from the north or the east,” terminating at either Union Station or a nearby location.

Rail tunnel construction has proven a pricey undertaking in recent years, ballooning the budgets of Toronto’s Eglinton Crosstown light-rail line and Ontario Line subway plans as well as Ottawa’s Trillium Line.

The Eglinton line’s budget soared beyond $13 billion from an initial $5-billion estimate, due to a slew of complex challenges that included moving gas and water pipes. More than 10 kilometres of the 19-kilometre Eglinton line are underground. The bill for that project works out to nearly $700 million per kilometre.

For Montreal’s Blue line metro extension, it tops $1 billion per kilometre.

So would the cost of a high-speed rail tunnel through Montreal, said Ahmed El-Geneidy, a professor at McGill University’s School of Urban Planning.

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At that rate, the proposed tunnel would account for between 12 and 18 per cent of the project’s budget, estimated at $60 billion to $90 billion.

“It’s very hard from a civil engineering standpoint and from a safety standpoint,” El-Geneidy said.

“We’re not talking about the standards of the 1900s when we built the Mount Royal Tunnel.”

The government has not yet made a final decision approving funding for the entire rail line.

Construction of the first phase of the 1,000-kilometre corridor is set to kick off in 2029 or 2030, linking Montreal and Ottawa in an effective test case for a massive infrastructure project intended to transform rail travel in Canada’s most densely populated region.

The proposed network would host locomotives running on dedicated electric tracks at speeds of up to 300 km/h, slashing current travel times. It would make for a three-hour trip between the country’s two largest cities and less than one hour between Montreal and Ottawa. Some 20 to 30 departures are expected daily on the Montreal-Toronto segment.

In its recent update, Alto said it is weighing two possible corridors between Ottawa and Peterborough, Ont. One is a more direct line between the two cities and the other curves south, closer to Lake Ontario.

The first option “reduces travel distance and community impacts but involves complex work in remote and sensitive areas” where rock formations make for slower, costlier construction, the update said.

The second simplifies construction, but runs through densely populated areas.

Either way, the number of stations — seven — remains unchanged. They are planned for Toronto, Peterborough, Ottawa, Laval, Que., Montreal, Trois-Rivières, Que., and Quebec City.

Transport Canada decided on the stations before a business case specifying the precise route, budget, ridership forecast and fare projections was presented to the public. One is expected in the coming years.

The stations alone mark a major cost.

Those above ground require about 42,000 square metres, “about the size of six football fields,” according to Alto.

In Montreal, the stop will be at Central Station or a spot nearby — above or below ground — CEO Martin Imbleau told The Canadian Press in an interview last week.

The rough route charted so far would see some 72 trains daily integrated into corridors that currently house rail and power lines, roads and highways, on top of the fresh-cut tunnels.

Rail bridges will also need to be built across the Ottawa River and the Rivière des Mille Îles that borders the north end of Laval, an island suburb north of Montreal, Alto says.

A three-month public consultation for the corridor kicked off last week.

A C.D. Howe Institute study last year found that the promised line would generate between $15 billion and $27 billion in value for Canadians over six decades, or less than half of the minimum cost of the project at best.

Alto’s projections are one or two orders of magnitude higher.

It says the rail service could generate up to $24.5 billion economic impact each year, equivalent to 1.1 per cent of Canada’s economic output and amounting to $1.5 trillion over 60 years.

The line would create more than 50,000 jobs during construction and require thousands of staff to run it afterward, the Crown corporation says.

This report by The Canadian Press was first published Jan. 20, 2026.

Christopher Reynolds, The Canadian Press