The span to be built by the federal government is slated to open in 2021.
The province says Ottawa should contribute to the rail project's potential $1.5 billion to $2 billion price tag, as it has on similar projects in Ontario and British Columbia.
The 15-kilometre service would connect Montreal's downtown to a major shopping development on the south shore. The line of seven to eight stops would take less than 20 minutes to complete and ease bus traffic on Canada's busiest bridge opened in 1962.
The rail system is expected to carry 32,000 passengers an hour in each direction, compared to 22,000 who now cross on dedicated bus lanes that were installed as a temporary measure in 1978.
Transportation Minister Sylvain Gaudreault said the province has committed $28 million to conduct feasibility studies and other prepatory work.
Ottawa hasn't shown an openness in the past to the idea, saying Quebec would have to use existing pools of infrastructure funding.
Municipal mayors and the Chamber of Commerce president who attended the provincial announcement said the rail project is essential for the region's economic development.
Railway manufacturer Bombardier (TSX:BBD.B) welcomed the province's commitment to a project that has been discussed for years.
"We feel that we're getting much closer than ever before and we feel that it's going to be done," said spokesman Marc Laforge.
He said the company would definitely be interested in bidding on the project which could be similar to Vancouver SkyTrain or systems in Kuala Lumpur and Seoul.
Depending on the type of system selected, it could carry about 29,000 passengers per hour using a four-car train, he said.
In addition to using its Canadian design centres, Bombardier would likely devote several of its manufacturing sites to the project, including one in La Pocatiere, Que., that will build the city's new subway cars.
Should the project get final approval, Bombardier would likely face stiff competition from global rivals such as Alstom, its partners on the Metro project.
— With files from Pierre-Saint ArnaudSuggest a correction