In the clearest sign yet that Ontario is losing patience with Bombardier, the government has privately signalled it is open to commissioning vehicles from other companies for a key Toronto transit project.

The Quebec-based company is contracted to provide 182 vehicles to Metrolinx for light-rail lines in Toronto. But Bombardier has struggled with persistent delays in producing a prototype for testing, and the government is showing new willingness to look elsewhere for part of the order.

According to industry and government sources, the three consortia competing to build an LRT along Finch Avenue West were recently offered the option of including vehicle procurement as part of their bids. This is a blow to Bombardier – whose Metrolinx order was to include about two dozen vehicles – and could let other manufacturers get a foothold in the Toronto area.

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Although it is not clear how easily Metrolinx could change the contract with Bombardier, other companies that are already building light-rail vehicles for the Canadian market expressed strong interest in the possibility of joining one of the three consortia competing for the project bid.

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"We'll be aggressive and very active on it," Patrick O'Neill, head of Siemens mobility division in Canada, said in a telephone interview from Germany.

"We would certainly like to break into the market in Eastern Canada. We do have market share in Alberta, but we'd certainly like to see some of that in Toronto and Ontario as well."

A spokesman for Bombardier suggested the company would refuse to give up any part of its order.

"Bombardier signed a contract in June 2010 to supply 182 [light-rail] vehicles to Metrolinx," Marc-André Lefebvre said in an e-mailed statement. "And so, we will manufacture and deliver 182 vehicles to Metrolinx, as per our contractual obligations."

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The Finch light-rail line is to run 11 kilometres from a future station on the Spadina subway extension to Humber College. Construction is due to start next year, and the line is scheduled to be operational by 2021.

The deadline by which the three competing consortia must submit their bids was quietly extended recently from October to February. Sources said this was partly to give the competing companies the option of adding a company that produces vehicles to their bids.

Robert Pattison, senior vice-president for light-rail transit at Infrastructure Ontario, said the extension was primarily about making sure the bidders have time to gather information needed to compile their proposals. He referred questions about vehicles for the line to Metrolinx, which would not make anyone available for an interview.

"We continue to explore all options," Metrolinx spokeswoman Anne Marie Aikins said in an e-mail. "No decisions have been made at this time."

It is not clear whether the deadline extension would give the consortia enough time to add vehicle procurement to their proposals. Bombardier could still be chosen, but other companies are keen to get a piece of the action.

"If the market does open to other vehicle vendors we clearly want to participate in the tendering and procurement process," Angelo Guercioni, country managing director for Alstom, said from Montreal. "If these opportunities do open up, Alstom will be gladly participating in that process."

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Bombardier's reputation as a vehicle manufacturer has been undermined in recent years. It has struggled to build reliable streetcars for the Toronto Transit Commission, has repeatedly adjusted its delivery schedule and has missed several deadlines to complete the pilot vehicle – a test model that precedes full production – for the Metrolinx order.

At the end of August, Bombardier promised the pilot vehicle to Metrolinx within a few weeks. It has not yet arrived, but Mr. Lefebvre said it has been assembled and Metrolinx has toured the vehicle, which he said is now being tested.