Well, a tip I can offer the OP (FWIW) is that I have found Fish&Wildlife Services tend to be trained as traditional law enforcement officers, and thus tend to take this approach even to social problems. While I doubt any government agency sprang into action based on a single phone call, it doesn't surprise me that closing access would be their idea of a simple solution to a complex problem.
I think with some level of citizen involvement you can get this area reopened. But if there isn't sufficient volunteerism from the locals you can hardly expect DFW to expend resources trying to shoo away undesirables.
For those that decry the enhanced rights of squatters and the homeless, now you know how respectable people feel when shopping at Walmart and being told here to be considerate of the people sleeping in the parking lot. Enhanced priviledges tend to make people more militant, not more cooperative.