I guess that would certiainly be possible. I was just there two weeks ago and really did not notice anything out of the ordinary -- most likely due to that area being in total seclusion (look at the above shot) from the rest of the park -- but I guess it is certainly feasible - but until I see a release from SF I'm not putting any money down.
Not too mention Real the 'enhanced red dots' on that main photo that could be plotted from anywhere ... and not any kind of official marker. Some of those pictures referrenced really could be anything ... even marking for a new sprinkler system.