Years back the SP set up the signals to be viewed from the right hand side of the locomotive cab. This was the case with the signals on Donner.

The track in the top picture is 2MT-CTC, so trains can operate on signal indication on either track in either direction, and thus the signals were set up for that, as well as to be viewed from the right side of the locomotive cab.

In the 2nd picture, the signals are setup as current of traffic, and thus only 1 track is signaled in each direction. They have set the signals up again to be viewed from the right hand side of the locomotive cab, only this time they just needed to do it for a single track in each direction. This trackage was also left hand running, so the signals ended up physically being back to back. Signal 2279 governs the track to the left.

After the UP changed the signal systems on Donner, the track from East Truckee to West Reno, which would include the area at signal 2279, has now become "Controlled Block System" in UP lingo. Basically it is bi-directional ABS signals, with full CTC still in the future.