In a hotly-worded letter to regional public affairs manager Robert Hest of Moncton, Mayor Williamson said he was "thoroughly disgusted with (CN's) action" against Wesley MacDonald, 60.
MacDonald, a 42 year employee, was the only member of a four-man crew aboard the train when it careened off a curve on March 9 where a downhill spur line meets CN's main line near here.
He suffered only minor head bruises when the two locomotives and 26 cars derailed, spilling about 2,000 litres of lead-zinc concentrate.
MacDonald was blowing the train's whistle to warn motorists as it traveled at about 100 kilometres an hour -- several times the train's normal running speed on the line -- through two level crossings.
Within days of the derailment, MacDonald said he began serving a six-month unpaid suspension. A conductor and two brakemen, who left the runaway train, received four- to six-month suspensions.
The mayor said he does not know how MacDonald could have been suspended.
"How could CN be so crass as to suggest his guilt after he risks his life to stay with the locomotive until it derailed?" asked Williamson in the letter.
"The man is alive," said Williamson. I wonder what would have happened if Wes had been killed in the derailment...I believe you probably would have nailed him to the cross as guilty even if he had died."
Although he disagrees with the suspension, Williamson said he is not attacking CN's right to discipline and added that the railway will never be able to convince the public that the decision was fair.
Citizens have told Williamson that they don't feel the decision was a just one, he said.
The engineer has spent his life working for the railway and has a good record, said Williamson, who said the suspension, coming just months before his retirement, will have an effect on his pension, which is based on his peak earning years.
"It's unjust and cruel punishment."
The mayor has also sent a letter to the Chancellory of Orders and Canadian Decorations in Ottawa, supporting MacDonald's nomination for a bravery award.
MacDonald is being considered for one of three national bravery award categories, said Danielle Dougall, chief of decorations.
The Canadian decorations advisory committee will recommend to Governor-General Jeanne Sauve within the next few months whether MacDonald is eligible for the Cross of Valor, Star of Courage or the Medal of Bravery.
Dougall declined to reveal who nominated MacDonald but did say it was a New Brunswick resident.
Meanwhile, both CN Rail and the Canadian Transport Commission have completed their investigations into the derailment. The railway is uncertain whether it will make its report public, while the CTC will make its findings known within the next few months.
CN earlier confirmed it suspected brake failure as the cause.