Two senior executives at the TTC are out of a job in a shakeup on the eve of Toronto's transit agency revealing the extent of problems with the Spadina subway extension.

Toronto Transit Commission head Andy Byford said in a memo to staff Thursday that he had decided a change of leadership on the project was needed "after lengthy and careful consideration."

Exiting the TTC are Andy Bertolo, who had been chief project manager for the Spadina extension, and TTC chief capital officer Sameh Ghaly. The terms of the departure were not released.

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Mayor John Tory released a statement saying a stronger culture of accountability sometimes meant personnel changes.

"TTC CEO Andy Byford has my full support in his efforts to restore public confidence in the management of the Toronto York Spadina Subway Extension. Torontonians have a right to expect better," he said.

The extension of the Spadina subway has been plagued by delays, mission creep and cost inflation. A report detailing various cost and schedule options for Spadina will be made public Friday.

"I think some of them are not realistic or palatable at all," said TTC chair Josh Colle. "The decision will be made by the commission and in turn council. Certainly my commitment, I know the mayor shares this, we're going to push for what it takes to fix this situation."

The report will be discussed at the TTC board next week. In his memo, Mr. Byford said that he would be outlining "next steps" around project management, reporting relationships and expectations for the project in the days after that meeting.

Problems extending the Spadina subway northward – a project that was originally expected to finish in 2015 but is unlikely to be operational before 2017 – have long been brewing. There have been weather-related delays and more time lost after a worker died on the project. What was to be a $1.5-billion project was also expanded further north, boosting the price to $2.5-billion.

A recent report in the Toronto Star said the project was at risk of going $400-million over that later budget. That number has not been confirmed by the TTC and the figures in Friday's report are expected to be lower. The final cost will depend on a variety of factors, including how urgently the city wants the work done and whether to complete the whole line.

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One possibility that has been studied is ending the line, at least temporarily, at York University. This would reduce its length and price at minimal cost to its ridership potential. But this idea runs counter to the wishes of provincial Transportation Minister Steven Del Duca, who represents Vaughan, where the line is to terminate if built in its full form.

The troubled project will be steered on an interim basis by Tony Baik, who had been the deputy chief project manager on the extension. The change is effective immediately and Mr. Baik will report directly to the CEO.

Mr. Bertolo and Mr. Ghaly "are no longer with the organization," said spokesman Brad Ross, declining to confirm whether they had been fired or had a chance to resign.

According to the Byford memo, Mr. Ghaly's role will be filled Susan Reed Tanaka, who was most recently head of engineering.

In a separate e-mail Thursday to the board, Mr. Byford informed the TTC's commissioners of the staffing change.