A vehicle system comprises an interface assembly and a controller both on board a first rail vehicle. The interface assembly comprises one or more mechanical couplers, fuel couplers, fluid couplers, and electrical connectors, to detachably couple the first rail vehicle to a separate, adjacent fuel tender vehicle, for the transfer of one or more of fuel (e.g., compressed natural gas) from the fuel tender vehicle to the first rail vehicle, heated fluid from the first rail vehicle to the fuel tender vehicle (e.g., for regasification of liquid natural gas stored in the fuel tender vehicle to the compressed natural gas), or electrical power and/or control signals between the first rail vehicle and the fuel tender vehicle. The controller is configured to at least partially control operations of the first rail vehicle in relation to interfacing with the fuel tender vehicle for fuel transfer, heated fluid transfer, etc.