Toronto's council voted Tuesday to back the Ontario Line, even after critics warned unanswered questions remain about the provincial proposal.

Councillors debated the new transit agreement between the city and province — one that's publicly supported by Mayor John Tory — during their monthly meeting. They voted 22 to three in favour of the plan.

The deal would see Toronto support the Ontario Line, a 15-kilometre route first proposed by Premier Doug Ford's government back in April, in exchange for the province dropping its plan to take over the city's existing subway network.

"I think the Ontario Line is full of potential," said Coun. Josh Matlow on Monday. "It's exciting. The way that it's extended and expanded past what the relief line vision was is terrific."

Despite that excitement, Matlow is also among those raising questions about the plan's logistics. Key details about the technology, route alignment, and feasibility are still up in the air, he suggested.

BREAKING: Toronto's city council votes 22-3 in favour of new transit agreement with Premier Doug Ford's provincial government, which sees province backing off subway upload in exchange for city support of priority projects like Ontario Line. <br><br>Background: <a href="https://t.co/KkbMlyXxmD">https://t.co/KkbMlyXxmD</a> —@LaurenPelley

"This is the problem with how transit is often done in Toronto and Ontario," he said. "Big announcements are made and then they do reality checks later."

A recent report to council from City Manager Chris Murray digs into what is known — and what remains unclear — about the plan, which would see a mix of underground and above-ground track stretching from Ontario Place in the west, through the downtown core, then north through the east end to the Ontario Science Centre.

In September, Metrolinx's board endorsed an initial business case for the line, sending it to the preliminary design stage. Murray's report notes the Ontario Line is currently at a 0 per cent to 10 per cent design level.

The total capital costs for the project could be between $9.5 billion and $11.4 billion, according to that first business case, Murray's report continues. But those numbers could change dramatically, with industry standards suggesting a difference of up to 100 per cent more at the high end, which equals a doubling of the cost.

Toronto transit expert Steve Munro said when it comes to the line's financial details, there's another piece that's unclear: how much the city will be paying over time to operate it.

"Sure, that's eight, 10 years down the future. But what are we getting ourselves on the hook for in terms of future costs?" he questioned.

The province is aiming to launch a request for proposals as soon as summer 2020, which a goal of having the line up and running seven years later.

"Given the current stage of the project and the early state of design and development, the City and TTC are unable to assess the validity of the stated timetable or the estimated cost at this time," Murray's report reads.

Metrolinx released this map of the proposed Ontario Line, which could include 15 stations. (Metrolinx)

Questions, concerns over route and technology

Munro also warns any changes to the proposed route alignment could throw another wrench in the timeline.

Recently, residents from east-end neighbourhoods like Leslieville spoke out at city hall, raising concerns about above ground portions of the line, which some claimed could lead to unhealthy noise levels, home expropriations, or reduced park space along the tracks.

Tory wants the province to mitigate those concerns, but Munro said doing so could balloon costs and create delays. "Switching from above ground in Leslieville to below ground, who pays for that change?" he asked.

Matlow said many of the city's questions are focused on the train technology which will be used for the Ontario Line — and how it works.

What's known right now, according to Murray's report, is that Metrolinx is proposing using 100-metre light rail trains, but the provincial agency has "indicated this will be determined through their procurement approach."

Similarly, the tunneling technology isn't yet confirmed, leaving questions about how the province's eventual pick would fare in a harsh Canadian winter.