The men were being treated in hospital and two of the employees were reported to be in critical condition.
Edmonton Police Staff-Sgt. Rob Mills said the men were using snowblowers and wearing hearing protection. They didn't hear the approaching train, which sounded its horn and hit the brakes as it slid towards them along the icy tracks.
"The train came along and saw them close to the track and tried to do some emergency braking, but unfortunately struck the three employees," Mills said.
"All three were taken to hospital."
Police said the east-bound train was going about 40 km/h.
The men are employed by A & B Rail Services Ltd. and were working under contract to CN.
Managers at A & B Rail Services were not immediately available for comment.
The collision is being investigated by CN, Alberta's Occupational Healthy and Safety Department and federal safety regulators.
The Transportation Safety Board is also sending a team of investigators to the site of the accident to assess what happened.
Patrick Waldron, a CN Rail spokesman, said the company's probe will include a review of its operating procedures, including safety.
"Obviously there are procedures in place for any workers, whether they are contract or regular workers, when they are out in the field," Waldron said from Chicago.
"What happened this morning is under investigation so we can find out all of the answers."