Did Southern Pacific ran their trains left-handed, like C&NW
Not in double track territory as far as I know. However, left handed running was possible using track permits or in earlier times train order authority to run against the current of traffic.
SPer Did Southern Pacific ran their trains left-handed, like C&NW
The Southern Pacific normally used the right hand side for their main lines with exceptions in the mountains. The #2 track on the Roseville sub from Rocklin to a cross over near Applegate was left hand running and still is today on the Union Pacific. The tracks are separated in some areas but do come back together and they run left handed on these portions. The main line out of Reno to Truckee and up to the big Hole tunnel is still left hand running also. The left hand running was used since the newer # track reduced the uphill grade.
CZ
The picture below is the cross over in Rocklin eastbound to start left hand running to Applegate.
This picture is at Newcastle at a point the tracks are together and use left hand running.
This is a westbound freight at Truckee running the left hand portion.