Assorted employees of the PRG, who would be in the know as to that sort of thing. If DFA is not mistaken, Gary Rall (PRG owner guy) is heavily involved in the push to open Madrone, so the information would most likely have come from him. Also, a few acquaintances of the Doctor have been heading out there lately, and have encountered no hassling, ticketing, or quarrying.
So now you know what Dr. Flash Amazing knows (well, to be sure, an infinitessimal sliver of what DFA knows, but you are, at the very least, up to speed on Madrone Wall access rumors); you may do with the information what you wish.