A Boise locomotive maker has won its fight to keep a foreign competitor from winning an exemption to the Buy American Act.

That leaves MotivePower Inc. as the only company with a viable bid to build at least 28 engines for Massachusetts commuter trains - a contract worth hundreds of millions of dollars.

The federal government Friday rejected a requested exemption to the Buy American Act from the Massachusetts Bay Transportation Authority. The authority requested the exemption so it could consider a competing bid from Vossloh Espana S.A., a Spanish unit of a German company - and the only other bidder.

The Federal Transit Administration said the Massachusetts authority must comply with the Buy American Act because it is using federal matching funds to buy the diesel electric engines, which it needs to replace aging units in its fleet of 80 locomotives. The act requires transit agencies buying new equipment to demand American assembly and 60 percent American parts when using federal matching dollars.

MotivePower, once part of Boise's former Morrison-Knudsen construction company, builds train engines at its manufacturing plant off Federal Way in southeast Boise. A subsidiary of Pennsylvania-based Wabtec, Motive Power employs 700 people in Boise.

"This is very exciting news for us," said Mark Warner, vice president and general manager of MotivePower. "It's a significant contract. With the options, it's worth about $280 million."

At a time when many companies are shedding jobs, Warner said the contract would allow MotivePower to "maintain current employment levels for quite a while."

The bid called for 28 locomotives, with an option for another 28.

The federal government is expected to pay 80 percent of the locomotives' costs. The purchase is part of a longstanding promise to improve service for the 72,000 people who take the commuter rail daily, according to the Boston Globe.

"MBTA has not established sufficient grounds for a public interest waiver," FTA Deputy Administrator Sherry E. Little wrote in a letter Friday to the Massachusetts authority.

"MBTA has not argued that this procurement involves the introduction of significant new technology. Nor has it stated how a waiver would benefit the riding public."

MBTA would not say Friday if it would award the contract or re-open the bidding process.

"Our procurement team will meet on Monday to discuss the MBTA's options, and decide what future course of action is in the best interest of the authority, fare-payers and Massachusetts taxpayers," MBTA spokesman Joe Pesaturo said.

Idaho Sen. Mike Crapo, Rep. Mike Simpson and Boise Mayor David Bieter had asked that the FTA deny the exemption because it could cost hundreds of American jobs in Boise and across the country.

"We must protect jobs for Idaho families," Crapo said Friday. "It would be a travesty to use American taxpayer dollars and a loophole in American law to allow this sophisticated technology and the jobs related to it to be lost to overseas competitors."

Simpson, whose district includes the Boise plant, said, "This decision affirms our belief that MotivePower and its Idaho work force produce a superior product and are rightfully entitled to the protections of the Buy America Act."

Mayor Dave Bieter said, "This is great news not just for MotivePower and for Idaho but for American jobs in general. I'm pleased that the FTA saw the wisdom of allowing U.S. companies to compete fairly."

Brad Talbutt: 672-6737