I would have to check, but I believe yesterday was one of the absolute MofW Windows/Curfews on the UP Fresno Subdivision where nothing could get through all day. The area you refer to is called "Haggin Wye" or just Haggin in the UP Timetable. All Main Tracks in this area are CTC, operated by the UP Omaha Dispatcher. In this case, the train would have pulled west of Haggin, then the Dispatcher would have lined the route to go North on the UP Sacramento Subdivision and yes, there was more than likely a locomotive on the back being operated in DPU Configuration that the Conductor rode on to observe and direct the Engineer doing the backup move. Once they were completely on the Sacramento Sub. the conductor would have gotten a van ride to get back on the lead locomotive to go south. It should be noted that 3 of the Amtrak San Jauquin Trains have been doing this exact same move, if you look in the service interruption page on the Amtrak Website, it expains wich Mondays those trains are doing it. Hope this is helpful.