Montreal's regional transit agency says it's prepared to file an injunction with the Essential Services council to prevent commuter-rail lines from being shut down if there's a CN Rail strike.

The Deux-Montagnes and Mont-Saint-Hilaire lines would be knocked out if engineers make good on a pledge to walk off the job on Saturday, the Agence Metropolitaine de Transport tells CTV News.

CN Rail and the Teamsters union are holding 11th-hour talks in Montreal Friday to avert a strike by the 1,700 engineers, who issued a 72-hour strike notice Wednesday.

"Given that we cannot currently predict the status of negotiations between CN and its employees, the AMT recommends that passengers ... prepare alternate means of transportation such as car-pooling or local bus service," says the agency.

"The AMT is currently trying to organize bus shuttle service."

Deux-Montagnes and Mont-Saint-Hilaire would be the only lines affected by a strike because the other routes run on Canadian Pacific lines.

AMT spokesman Pierre Luc Paquette says his agency will work with transit corporations throughout the region to ensure that next week's commute is not disrupted.

Paquette says that CN has maintained commuter rail service during past labour disputes and he hopes the same thing will happen this time around.

The Deux-Montagnes and Mont-Saint-Hilaire lines carry more than 37,000 passengers per day.