The province's proposed Toronto subway relief line alternative, the so-called Ontario Line, is likely only at the two per cent mark for design work, city councillors heard from TTC staff on Tuesday.

But even as concerns about potential delays and unknowns grow — with one councillor dubbing it the "Mystery Line," as city officials remain in the dark on the timelines and cost breakdown — the Ministry of Transportation plans to submit a business case by the end of June.

"The provincial government doesn't know what the hell they're doing," said Coun. Joe Cressy, a critic of the province's transit plans, during an interview in council chambers.

The downtown relief line was already at 15 per cent design, he noted.

TTC and city staff told council it took a full year to get to that point, which also followed years of planning beforehand and an environmental assessment, which has not been completed for the longer Ontario Line.

With those details in mind, Cressy said the 15-kilometre line stretching between Ontario Place and the Ontario Science Centre would take longer to build — despite the province's belief it will be delivered by 2027.

"It means more people packed into subways waiting for transit relief," Cressy said.

The new details emerged on Tuesday as council discussed the city's ongoing talks with Premier Doug Ford's government over the province's plans to expand, and eventually take over, Toronto's subway network.

TTC staff told councillors the discussions have included looking at around 40 possible alignments for the line, which has since been whittled down to around four.

Previous details from the province note the project would be "largely consistent" with the north portion of the relief line, stretching from Pape station to a new terminus at the Ontario Science Centre, and extending from a planned west terminus of Osgoode station through the King and Bathurst area to a new terminus Ontario Place.

In response to questions from CBC Toronto, Ministry of Transportation spokesperson Andrew Buttigieg did not provide details on the specific alignments being considered or the level of design work completed so far, but the ministry is working to submit a business case "at the end of June," he said.

"The Ontario Line is currently in the planning, design and engineering phase," he said in the statement.

Councillor calls for release of 'secret information'

According to the province's budget, the "freestanding" line would not share a track or resources with the subway system, and would use a lighter, more modern and cheaper trains.

In council chambers on Tuesday, Coun. Mike Colle pressed TTC staff on what they know about "secret information" regarding the technology under consideration for what he called the "Mystery Line."

"The specific technology has not been identified," responded TTC CEO Rick Leary.

City and TTC staff also told councillors they have yet to see the province's timelines or cost breakdown for the project, which the province previously has said costs roughly $11 billion in total.

"The City's previous planning on the relief line is being utilized and we're working with Infrastructure Ontario to look at new, innovative ways to get transit built faster, and at less cost," Buttigieg said.

While some members of council are questioning those claims, and whether the city should remain at the table given all the unknowns, Mayor John Tory insisted the city needs to "move forward with the process" of getting answers to the city's more than 60 technical questions on the transit plans.

Following his remarks to council, councillors overwhelmingly rejected a motion from Coun. Josh Matlow to break off talks tied to a subway upload in a vote of 7-19.

Speaking on behalf of his motion, Matlow said it's all just a "one-sided discussion."