To go into 3/10 you just need to go into the Press office and ask to sign a waiver and get your wrist band endorsed. The head corner worker at 3/10 will ask to see your wristband.
They asked me a lot more questions the first time I did it then the subsequent times. Once they've seen you a few times they'll pretty much just let you sign the form and go.
I'm not sure how you get permission to go anywhere else. There was a guy on the inside of 9 coming down the hill, you can see him in some of my pictures. Being that close to the track on the inside is very challenging but I bet he got awesome pictures.
I would assume as long as no one does anything stupid they will continue to be pretty cool about it.
Ben