They are being done as a favor by ScaleTrains for FVM since, they are no where close to be able to produce their own locomotives at the new factory. UP 1943 has been shelved until a later date as well.
A close stand in is a far fetched idea. The only one close to actually being close would be 8520, but 4000-4005 have major differences between addition of inverter box, GEVO cab, and the front steps are 6, and the rear steps are only 5. Of course 1700-1701 are EMD SD70ACCs, think that is enough said.
It really is no different than when FVM was going to do these on their ES44AC molds.
I wonder at what cost this well be then for modelers that were holding out for the correct ST versions as they have said they were going to do them at some point.
Chris