A more prototypical UP Mof W train would be all ballast or all rail or all ties, etc. the type of train you are suggesting would be closest to a "wrecker protection" train that would respond to derailments. It would have a several cars of ballast and a couple flats of track panels (not rail but built up panels). An MP15 would only be used in a terminal, out on the road or if it operated any distance it would have a GP38, 40, 50 or 60 or and SD40, 60 or C40-8.
The UP uses both GSC type cast flat cars and more modern straight sill flats. Here are pictures of flats with concrete ties. they have been modified with "bulkheads" to retain the ties and rails along the sides for the tie cranes to move the ties up to the automated track renewal machine (TRT909).
Dave H.
Dave H. Painted side goes up. My website : wnbranch.com
I was planning on modeling the train in the video, exept id add a hopper full of ballast.