Not sure how well this applies out here, but back in the Northeast (Albany, NY area), there are a lot of gated caves. I believe this is because they were bought by the NCC (Northeastern Cave Conservancy), and is considered private access. If you're a member of a local grotto, it's not hard to learn who you need to talk to in order to get the keys.
Although for here in OR, if the gates are locked now, does that mean they won't open them up even in the off-season? (or are there even gates?)