CTV News has learned CN is reviewing a section of rail line that's been losing business in New Brunswick.

CN owns the rail lines between Halifax and Montreal and the company uses the mainline to haul freight. Via Rail Canada, a Crown-owned passenger service, pays rent to CN to use its rails.

Once past Moncton, there are two rail lines through New Brunswick and CN uses its shorter, faster route through the province.

Via Rail uses the CN line from just outside Moncton, which snakes along the northeast to Campbellton and into Quebec before it joins the mainline again on the shore of the Saint Lawrence River. And that line is in trouble.

"We're seriously re-evaluating the line," says Julie Senécal, manger of CN Public and Government Affairs. "We always do that at CN for all the lines we own, but on this line, the volumes are extremely low."

There are significant differences in the two lines. The mainline through New Brunswick is much shorter than the one used by Via Rail, and the quality of the rail line is also much higher.

The maximum speed on the mainline is 80 kilometres per hour, while the maximum speed on the rail line used by Via Rail is only 50 kilometres. A CN official says there has been no growth on that line, and that has Transportation Minister Claude Williams concerned.

"We recognize there is a slowdown in traffic on the line and that certainly raised concern for CN," says Williams. "It's always a concern when there's a possibility of diminishing in terms of that infrastructure."

CTV News has learned that even the CN mainline from Halifax to Montreal is underutilized, as it frequently operates at about 30 per cent capacity.

At this point, Senecal says that while the line is under review, no decisions have been made.

Eastern New Brunswick has lost a few paper mills in the last few years, and the Brunswick Mining & Smelting Corp. – a major customer on the eastern route – is expected to close in 2013.

Senécal says that will make Via Rail the last big customer on that line. She also says that if CN makes a decision, it will be made public and require public input.

With files from CTV Atlantic's Rick Grant