The rail workers' union, Teamsters Canada Rail Conference, announced months of negotiations broke down with CN "unwilling to address safety issues".

According to the union, CN currently requires members to operate trains alone from outside of the locomotive, hanging on to moving trains with one hand while operating a remotely controlled locomotive with the other. Railroaders are expected to do this in rain and in freezing temperatures, sometimes for distances of up to about 27km.

The mining industry is one of Canada's Class I railways' biggest customers, consistently accounting for the majority (52.3% in 2018) of annual rail freight revenues. It is the single largest shipping group by volume, according to Mining Association of Canada (MAC) data.

Most of this production volume is shipped to international customers, together accounting for 20%, or more than C$105 billion (US$80 billion) of the total value of Canada's exports in 2018.

"A strike by CN workers will have a seriously harmful effect on the industry," said MAC CEO Pierre Gratton. "The shipment of fuel and other supplies to mine sites will be compromised as will the transport of mineral products."

The MAC called on the federal government to impose binding arbitration to address this dispute. "[Government should] also consider such arbitration as a required step in future labour disputes involving the Class 1 railroads, given the frequency and adverse impact of such disputes," Gratton said.

The government of land-locked Alberta, where the bulk of Canada's world-class crude oil reserves are held, called on prime minister Justin Trudeau to immediately recall parliament to urgently address the CN Rail strike.

CN ships about 170,000 barrels of Western Canadian oil per day.

"Any disruption in shipments would have serious consequences for an economy that is already dealing with severe bottlenecks due to cancelled and delayed pipelines. Alberta cannot see further restrictions on our ability to export our product," Alberta's Energy minister Sonya Savage said.

"Parliament is scheduled to return on December 5. Unfortunately, even this short wait could result in serious damage not just to the Alberta economy, but to the Canadian economy as a whole. We call on the PM to immediately call back parliament to enact emergency back-to-work legislation for CN Rail."

The Canadian Association of Petroleum Producers said it was concerned about any developments that could negatively impact the availability of rail capacity, particularly considering the current shortage of available pipeline capacity relative to oil production in western Canada.

"We will be monitoring such developments carefully to assess their potential impacts on Canada's global competitiveness. All modes of crude oil transportation capacity are needed to ensure Canadian crude oil producers have sufficient market access to serve the needs of Canadians as well as to access new, growing markets around the world," said CAPP VP for oil sands, fiscal and economic policy Ben Brunnen.

Alberta's Agriculture and Forestry minister Devin Dreeshen also said Alberta's farmers were impacted by the strike, since they were also depending on rail to get their products to market. "We have seen the severe consequences of rail backlogs before. Farmers don't need the added pain from compounding rail delays, especially after this difficult harvest. Now is the time to act."

With the miners expected to be hit hardest, the MAC urged the federal government to "take any and all action necessary" to address the work stoppage before it damaged the economy. The association also warned the strike action could have far-reaching consequences for the Canadian economy, including potential reputational damage as a reliable trading partner, a stable location for business operations and a competitive destination for business investment.

Federal Transport minister Marc Garneau urged both parties to continue their negotiations. "While we are concerned about the impact of a work stoppage on Canadians, we remain hopeful they will reach an agreement," he said.

The federals said it supported "and has faith" in the collective bargaining process, with the Federal Mediation and Conciliation Service assisting both parties since June.