Stadler has been building Diesel Multiple Units (DMU) and Electrical Multiple Units (EMU) for railroads all over for some time. They have various options for transit operations (light rail) as well as commuter rail. I have worked with them regarding the new DMU's built for the new TEXRail commuter rail operation in Fort Worth, TX. The vehicles were assembled in Salt Lake City. Stadler has also built DMU commuter rail vehicles for Cap Metro (Austin, TX) and Denton County Transportation (Dallas, TX). Other operations that are looking at Stadler are the Redlands, CA (Arrow) commuter rail project and CalTrain commuter rail (San-Jose-SF, CA) for their new by-level EMU vehicles. They are powered with either a Diesel or Electric "Power Pack" sandwiched between the A-B cars. If longer trains are needed, more power packs can be added along with "C" cars between the A-B cars. The power packs are very quiet and passengers can pass through them on the commuter rail cars.
MDR