UP PU3200A-6 958200Oakland CA Oakland

This engine appears to be built from a SD40-2. The loco trucks have Dofasco, the name of a Canadian steel company, cast into them so the original locomotive was probably built in Canada.

Here is a link to a Union Pacific site telling about the tie removal trains and with a video showing them in action: https://www.up.com/aboutup/community/inside_track/new-tech-rr-c..0.htm