Luminant owns the plant and the park. To my knowledge they will not entertain selling just the park, so it's a package deal for all the land around the lake and heck it may include the mine. If it hasn't expired yet, there was a lease on the park and the person that had the lease thought they could break even or make money on the entrance fee's and camping fee's. That didn't pan out, so the lessor is the one with the lock on the gate.
Luminant only owns the land around the lake, the plant and land with it was sold. It doesn't include the mine...Luminant typically holds them, plants trees, stocks ponds, etc...I've seen some of those mining properties go up for sale though. From my understanding, Luminant has the lock on the gate for liability reasons, it was open and leased for a period but not anymore.