Actually, LLPX #2236 was never a UP locomotive. Locomotive Leasing Partners (LLPX) just painted their locos that way.
LLPX #2236 was a former Long Island Railroad engine, purchased by the Metropolitan Transportation Authority new in 1975 (MTA was the NY State agency that ran the LIRR, Metro North, and NYC Subways). That GP38-2 hauled LIRR commuter trains until 2001, when LIRR got rid of all of its GP38-2s as the new dual-mode DM30ACs came on-line.
You can tell from the LIRR-specific set of features on that loco-- Square marker light mounts (which remain after they plated over the lights), handrails that do not quite go as low on the steps as engines on most other roads do, jumbo anticlimber on the front, plus the square jacking pad plates.
I have followed LIRR locos for years, for obvious reasons.
Hope this helps!