BNSF trains running from Denver to northern Colorado are not unusual. BNSF trains doing this on UP's Greeley Sub are unusual! Due to the closure of the Front Range Sub after flooding a week earlier, the Galveston, TX to Bonneville, WY (G-BNVGAT4-19A) "stinky slinky" molten sulfur train still needs to run. So, a BNSF road pilot (familiar with the Greeley Sub) got on board with a BNSF crew and took this train north.
In Cheyenne, the train will use the transfer track to move back to BNSF property and continue to Bonneville.