Canada grain farmers sue railways for overcharging

* Allege they were overcharged more than C$1 billion

* Filed in Saskatchewan court; suit needs court approval

* Second class action on same issue

VANCOUVER, British Columbia, Nov 6 (Reuters) - A small group of Western Canada farmers is suing the country's two big railways, alleging they have been charged at least C$1 billion ($934.5 million) too much for grain shipments since 1983.

The five grain producers filed the class action lawsuit against Canadian National Railway Co (CNR.TO) and Canadian Pacific Railway Ltd (CP.TO) in a Saskatchewan court on Oct. 15, court documents show.

A CN spokeswoman said the matter is before the courts and the company had no further comment.

CP is reviewing the suit, a spokeswoman said, declining further comment.

Since 1983 Canadian grain farmers' freight rates have been capped by the government, which allows CP and CN to charge rates that cover only their costs.

The suit alleges that both railroads claimed costs that were "ineligible or much higher than those incurred". It cites a 2007-08 Canadian Transport Agency review that it says found the railways pocketed C$72 million after charging three times too much for hopper-car maintenance.