From the Orange County (Ca.) Railway Historical Society newsletter, which in turn got the info from a member who sent in an Orange (Ca.) Daily News item:
The UP (former SP) is selling to homeowners 17 acres of abandoned right of way of the former Tustin Branch in the city of Orange. The line was originally built in 1888, and this segment of the line has been abandoned since 1969 when a bridge over Santiago Creek washed out.
The residents did not want a trail built on the section being sold because of fears of crime and other problems. In this area the line had run like an alley behind the back yards of homes on either side. [There is a trail a few blocks further south, where the line had paralleled a street and a creek].
I explored part of this r-o-w last summer; there were some No Trespassing signs so I did not head too far off into the tall weeds. It looked like it was used more for teenage “parties” instead of dirt bike riding or hiking.
MP