MONTREAL - Canadian Pacific Railway is evoking the possibility of another Lac Megantic-like disaster if it is forced to rehire a dishonest, drug-abusing locomotive engineer the company sacked in 2013 after he derailed a train while using cocaine on the job.

The engineer, who has had a history of absenteeism and a gambling addiction, tested positive for cocaine use after he derailed a train in a CPR Montreal yard in 2012, court documents state.

Because the 45-year-old man initially and repeatedly denied using cocaine, the company's lawsuit also cites his "dishonesty and deception" as a reason they don't want him back.

The Teamsters Canada Rail Conference union grieved his termination, calling it "excessive."

Quebec railway labour arbitrator Michel Picher last month ordered CPR to rehire the engineer, a move that stunned the company's senior management.

Picher ruled the locomotive engineer's long-time cocaine addiction -- the man now admits using since 1987 -- was a "disability" for which he had sought treatment and is now doing well. Thus, he deserves another chance, Picher ruled.

A furious CPR has filed court documents in Montreal to overturn the labour arbitrator's ruling, which the railway's lawyers called "manifestly unreasonable and unintelligible."

CPR lawyers note Canadian railways are obliged by federal law to carry hazardous goods, such as ammonia, chlorine and petroleum crude oil in tanker cars.

Because those obligations impose massive risks and liabilities on railways, they must also be free to terminate untrustworthy employees who flout safety rules, CPR lawyers added.

"The lives and safety of CPR's employees and the public at large are at stake ... CPR holds all its employees, including its locomotive engineers, to the highest safety standards," the company's lawsuit states.

"As the Lac Megantic derailment has recently shown, the failure of a locomotive engineer to follow safety guidelines and rules can lead to tragic and catastrophic circumstances."