Toronto and York Region are facing an additional $400 million in construction claims and other expenses on the overdue Spadina subway extension.

The costs would be split 60/40, with Toronto on the hook for $240 million and York Region facing a $160 million cost for the 8.6-km transit line.

The extension, from Downsview Station to the Vaughan Metropolitan Centre near Highway 7, is about 85 per cent complete. Testing will begin in April 2017 for an opening later that year, about two years after the originally scheduled launch.

It is now tracking to cost $3.2 billion, up from the most recent $2.8-billion budget, according to a TTC staff report released Friday.

CEO Andy Byford, who came to the TTC in 2012, has called the project "an albatross around my neck." But on Friday, he expressed relief and pride that the end is in sight.

"At the end of 2017, when this railway opens, it will be spectacular. It will be something Toronto and York Region can be very proud of," he said, following a media tour of construction at the York University Station.

Byford would not say exactly how much of the additional $400 million — a figure reported by the Toronto Star last March — was for claims, since the TTC is still negotiating with its six contractors.

He said he's confident in the accuracy of the figure, which comes from a detailed analysis by Bechtel, the engineering firm hired last year for $150 million to take over management of the project.

"Can I say with certainty that figure won't change? No. It could come in less than $400 million. Certainly that is what we're hoping to achieve. But because some of the claims will almost certainly go to litigation, I can't predict the outcome," he said.

It will be up to the city to figure out where the money comes from, but it will be accounted for in the capital budget. It will not affect fares, he stressed.

Virtually all major construction projects have claims, where contractors try to recoup the costs of design changes, scope or materials. In many cases a settlement is negotiated. When that doesn't work, the matter goes to litigation, which can take years. The Sheppard subway, which opened in 2002, still has an outstanding property claim.

But the Spadina subway has many claims related to changes to the complex station designs, which were modified and scaled back along the way.

"Ultimately if you cannot afford to build something that is architecturally spectacular, that should be built in at the start and not keep changing the designs," Byford told reporters.

The York University station, which features a signature boomerang-style roof built from curved steel, was the last site to be built and is the least complete, at only about 63 per cent.

But it is expected to be the busiest stop, accommodating about 30,000 riders a day.

The subway was supposed to open in 2015, but a series of delays, including a late flow of federal funds, meant the work, originally scheduled to start in early 2007, didn't get underway until late 2008. The schedule was never adjusted to account for that, said Byford.

"I could not turn the clock back to mitigate against the costs and the delays, due to the fact that the designs of the stations kept changing. I could not turn back the clock to mitigate against the fact that a large amount of the contingency funding was actually used to absorb the various schedule delays to the start of the project," he said.

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If an outside project manager hadn't done a re-set, the subway probably would not have opened until late 2018 or even 2019, said Byford, who last year fired two senior TTC executives who had been in charge of the Spadina extension.

Councillor Josh Colle, who chairs the TTC board, said he became aware of the delays and over-runs on the project only last March, although he had served on the TTC board previously.

"Every dollar in claims is a dollar that isn’t used to improve the daily commute of the people of Toronto," he said in a statement.

The city is reviewing the TTC's capital program and considering whether the transit agency should be in charge of large construction projects.

The head of Infrastructure Ontario, the province's agency in charge of public-private partnerships, including the Eglinton Crosstown LRT, said there are better ways to protect the public interest.

Bert Clark said TTC management appears to be handling the project with competence. But, "it inherited a series of construction contracts that do not appear to provide the public sector owner with sufficient protection. You can’t undo that now," he said.

Clark recommends against breaking up big projects into smaller contracts such as the individual station contracts awarded on the Spadina extension. He also says the builder should be responsible for design and design errors and contractors shouldn't be fully paid until construction is complete.