The Ontario government will announce Friday it's moving ahead with planning a high-speed rail line from Toronto to Windsor, CBC News has learned.

Senior Liberal sources told CBC News the government will begin preliminary design work for the 350-kilometre link and invest $15 million in a comprehensive environmental assessment.

Premier Kathleen Wynne will make the announcement in London on Friday morning, flanked by Transportation Minister Steven Del Duca and Deputy Premier Deb Matthews. Then she'll travel to Kitchener to make the same announcement at noon.

The project would use a combination of existing track and new rail lines dedicated to the high-speed train, officials told CBC News. It would include stops in Guelph, Kitchener-Waterloo, London and Chatham, and connect to Toronto Pearson International Airport.

On Friday, Wynne will make public a report from the government's special adviser on high-speed rail, David Collenette, a former federal minister of transportation.

Officials who have seen the report say it concludes there is a business case for high-speed rail along the Toronto-Windsor corridor and concludes there are opportunities for private-sector participation in financing and building it.

$55M per km

The report recommends a railway that could carry trains travelling 250 km/h and could be built at an estimated $55 million per kilometre, which would mean an approximate total cost of $19 billion. The report also examines a scenario for trains capable of travelling 300 km/h, but it would cost nearly three times as much ($149 million per km).

Collenette proposes building the railway in phases, completing the Toronto to London section by 2025 and London to Windsor by 2031.

The report says high-speed rail "would also create opportunities for regional development, help shape transportation planning in cities and towns throughout the corridor, and improve interconnectivity and mobility options across Southwestern Ontario," according to an excerpt provided to CBC News.

The government will create an arm's-length Crown agency to oversee the project, said officials. They also said the comprehensive environmental assessment will start this year but will take four to six years to complete.

A previous feasibility study for high-speed rail focused just on the Toronto-London corridor. Documents obtained by CBC News at the time put the infrastructure cost at $2.5 billion, and envisioned a one-hour, 11-minute trip from London to Toronto, carrying six million passengers a year by 2025.

Ontario's high-speed rail promises

Just days before the 2014 provincial election campaign, the Wynne Liberals trotted out a promise to deliver high speed rail service connecting Toronto, Pearson airport, Kitchener and London within 10 years. The then-minister of transportation, Glen Murray, indicated the service would run up to 28 times a day in each direction.

Soon after the election, the high-speed rail project slowed to choo-choo speed. The Liberals started hedging on the promise, refusing to commit to a timeline.

Documents obtained by CBC Kitchener revealed that the study underpinning the Liberal promise was rushed to be ready in time for the campaign, with the consultant surveying the route using Google Earth instead of from the ground.

In the fall of 2014, the Wynne government ordered an environmental assessment for high-speed rail corridor, then in October 2015, appointed Collenette as a special adviser on the topic. "Bringing high-speed rail to Ontario remains a steadfast commitment of our government," Del Duca said at the time.

The government has had Collenette's report for months, but is only making it public now.

Last month's 2017 provincial budget included a mere three sentences about high-speed rail.