ElectroMotive Diesel (the former Electro-Motive Division of General Motors) did enter into a marketing agreement with MotivePower Industries a few years ago to cross-market the GP15D and GP20D locomotives.
EMD sold the locomotives, MPI built them. I believe that EMD may have provided some sort of engineering support or maybe even manufactured some components of the locomotive, but the units were still built by MPI in Boise, Idaho. Sometimes they would carry a EMD builders plate, but it clearly stated the unit was actually built by MPI in Boise.
While EMD no longer lists the GP15D on their website they still list the GP20D as a current model
. HOWEVER - the picture of the Amtrak locomotive doesn't resemble the GP20D (very different cab design), and judging from this website
, looks like that the Amtrak locomotive had really nothing to do with EMD other than coincidential use of EMD design with regards to the trucks, cab, and probably prime mover, traction motors, and other components. They also clearly bear a MotivePower Industries builders plate
which means likely EMD didn't receive the order.
MotivePower Industries doesn't seem to offer much on their website