The entire spec for the magstripe on their tickets, and a preliminary spec for the new 2D self-print and phone tickets that are being introduced.
Edit: I have yet to obtain a valid 2D ticket myself, but the promotional image released is at least similar to what the spec describes, and the pre-amble is a match.
Please don't do anything illegal. It's not good for you (obviously!), and it eliminate any legitimate moral ground in the debate. We're trying to do what's right + good here, not to be underhand + malicious.
I'm pretty sure I obtained these documents legally, their webserver should have asked me for a password for the files but for some reason it did not (has since been fixed). They're under copyright though so I can't disseminate them.