MONTREAL -- Rail workers pushed back hard Friday against the federal government's move to put them back on the job, with a new strike notice and a regulatory challenge making it unclear when freight traffic will fully resume.

At Canadian National Railway Co., trains began to move again Friday morning as workers started to trickle back to work — even as the Teamsters union issued a 72-hour strike notice against CN shortly before 10 a.m. EDT.

And at Canadian Pacific Kansas City Ltd. — where operations remained shuttered — the union has challenged a directive for binding arbitration issued by Labour Minister Steven MacKinnon to the country's labour board.

A work stoppage at both national railways prompted MacKinnon to ask the Canada Industrial Relations Board on Thursday to use the mechanism, aimed at resolving an impasse that has halted freight shipments and snarled commuter lines across the country.

The labour board summoned the parties to a meeting Thursday night, followed by a hearing Friday morning.

The tribunal said in an email it is addressing the issue "with utmost urgency." A decision is expected later in the day.

In Calgary, picketers rallied outside CPKC's head office, where demonstrators received a visit Friday morning from François Laporte, president of Teamsters Canada.

Laporte and Sean O'Brien, president of the International Brotherhood of Teamsters — the union represents 1.4 million members across North America — arrived horns blaring in a black semi truck sporting "Teamsters" on the side.

O'Brien called the lockouts by both rail companies "a disgrace."

"This is not over. I'm telling you this is not over. The struggle continues," Laporte said to the 70-odd workers on hand.

CPKC workers went on strike at the same time the lockout came into effect early Thursday morning. CN employees are not yet in a legal strike position.

Before making the binding arbitration directive, the labour minister had faced pressure to intervene from business groups, which warned of the economic fallout caused by the work stoppage and urged Ottawa to break the deadlock and kick-start freight service.

At a Thursday news conference, MacKinnon said the government remains "committed totally to collective bargaining," but that the cascading effects of the shutdown demanded action.

"Workers, farmers, ranchers, commuters, small businesses, miners, chemists, scientists ... the impacts cannot be understated and they extend to every corner of this country," he said.

The government gave the negotiations "every possible opportunity to succeed," MacKinnon added.

Each side had accused the other of failing to negotiate seriously, with wages and scheduling as key sticking points. The union had rejected binding arbitration, framing Ottawa's decision as a move to "sidestep" its choice.

"The best way to have a contract is at the bargaining table. We don't believe in letting a third party decide what’s going to be our working conditions," said Laporte.

The Teamsters say both companies are angling to weaken protections around rest periods and scheduling, jeopardizing safety. CN also has its sights on a scheme to move some employees to far-flung locations for several months at a time to fill labour gaps, the union says.

CN pushed back on Friday, saying the Teamsters are "holding Canada hostage to their demands."

"CN is focused on recovery in order to resume powering the economy. The Teamsters are focused on returning to the pickets and shutting everything down again," said spokesman Jonathan Abecassis in a phone interview.

Canadian Pacific said Thursday night it was "disappointed" by the union's challenge before the labour tribunal. "CPKC remains prepared to resume service as soon as it is ordered to do so by the CIRB."

The minister's directive to the industrial relations board said the parties were at an "impasse," necessitating intervention. Binding arbitration would produce a settlement to "secure industrial peace" and protect Canada's reputation as a reliable trading partner as well as the affected sectors, from agriculture to energy, retail and manufacturing, MacKinnon wrote.

His directive, seen by The Canadian Press, instructs the tribunal "to order CPKC to resume operations" and workers "to resume their duties."

The language around resumption of duties might suggest that strikes and lockouts are off the table following a ruling from the board.

Earlier this summer, a looser directive from then-labour minister Seamus O'Regan during a strike by WestJet mechanics resulted in a ruling for binding arbitration. However, the tribunal also said the government never technically barred a strike, allowing workers to continue their job action until a deal was reached at the bargaining table following hundreds of flight cancellations.

In Calgary, Laporte said that as far as he is concerned the standoff will continue.

"Our people are still on strike," he said of CPKC workers. "We're still on the streets so our operations will not resume. It is not going to be business as usual for both companies."

O’Brien said the International Teamsters fully support their Canadian colleagues.

"Reward these workers with what they have earned. But also don't try to diminish safety," he said.

"What's important here is not to lose sight of the fact of who caused this problem right now. They chose to lock these workers out," O'Brien said.

"We got your backs 100 per cent."

This report by The Canadian Press was first published Aug. 23, 2024.

— With files from Bill Graveland in Calgary.

Companies in this story: (TSX:CNR, TSX:CP)