Ted,
There is a lake (rather Vasona Reservoir) but the RR does not go over it.
The trestle is over a small gulch on the shaded perimeter of one of the lawns on the Vasona Side. However, the other bridge (an SP piggy back flatcar) crossed just beyond the depot does cross Los Gatos Creek. It also carries pedestrian and bike traffic.
Below is a link to an old home video of mine from 1990 showing the 2-Spot. The engineer in the video is Chris Rody (sp), one of the paid "summer engineers" on staff when steam ran daily.