Spokesman Dan Stessel says the dual-mode engine is the first of its kind on any railroad in North America.
The locomotive is one of 26 purchased by a $310 million order in 2008 that was made with the now-defunct Hudson River commuter rail tunnel in mind.
The engines would have allowed trains on the Pascack Valley Line in Bergen County to go directly through the tunnel without switching to an electric locomotive as they do now.
Gov. Chris Christie cancelled the project in October.
Sixty percent of NJ Transit's tracks are not electrified.
Stessel says dual-mode engines using a combination track can switch to electric and save on diesel fuel.