MONTREAL - A decision obliging more than 9,000 Canadian rail workers to stay on the job is a win for the railways and could impact bargaining in other federally regulated sectors like aviation, the head of a Canadian rail workers' union told Reuters.

Paul Boucher, president of the Teamsters Canada Rail Conference, also said the union would work with other labour groups as it mounts a legal challenge to a Saturday decision that halted work stoppages at the country's two largest railways and imposed arbitration.

While the Teamsters will obey the order to return to work, the union has warned it could lead to the imposition of future contracts, eroding workers' bargaining power. The decision comes as Air Canada pilots press for a new contract and can commence job action as early as mid-September if there is no agreement with the country's largest carrier.

Air Canada said on Sunday its intent is to reach a negotiated settlement with the pilots over the coming weeks.

"Any federally regulated company, it's a win for them at this point," Boucher told Reuters in his first interview since the Thursday lockout. "This is disastrous for labour, for workers."

The Canada Industrial Relations Board made the decision after Labour Minister Steven MacKinnon asked it on Thursday to end an impasse in separate talks between the Teamsters, Canadian National Railway and Canadian Pacific Kansas City.

The dispute, which triggered a first-ever lockout of Teamsters workers on Thursday at both freight rail carriers, led to unprecedented disruptions that threatened to hammer Canada's export-driven economy, leading agricultural businesses to plead for relief.

Tim Perry, president of the Air Line Pilots Association Canada, which represents Air Canada pilots, said the union is concerned.

"The new Minister of Labour does not trust the Canadian laws governing collective bargaining, nor does the government he represents respect the constitutional rights of workers," Perry said in a statement.

A spokesperson for Canada's labour minister declined to comment on whether the decision to impose binding arbitration on railways would serve as a precedent in other sectors, including aviation.

CN has said the company would have preferred a negotiated agreement but was satisfied that the labour stoppage is over. Spokesperson Jonathan Abecassis said on Sunday that CN tried to get an agreement for nine months and made five offers that would have improved wages and working conditions but the union did not engage. A CP spokesperson said it regretted that the government had to intervene and fundamentally believes in and respects collective bargaining.

Both railways have said they are focused on restoring service, with the Teamsters calling off a CN strike on Monday but planning to appeal the decision in federal court.

Other unions could participate in court and support the Teamsters, Boucher said.

"This historical moment is so extremely important that labour needs to get involved and they will," he said.

The 58-year-old Boucher, who once worked as a CN locomotive engineer, has been bargaining with CN out of a second-floor conference room at a downtown Montreal hotel.

The Teamsters union disagreed with CN and CP over scheduling, shift duration and availability. CN, for example, wants employees to work up to 12-hour shifts, compared with 10 hours in the current agreement, a move opposed by the union.

Boucher said he has been in contact with the union representing more than 5 400 Air Canada pilots who approved a strike mandate last week.

"We're going to be calling on all labour across Canada to join our fight and take this all the way," he said.