I'm not in the know but I don't think it's ever been a legal trail, more so one that was known to exist and people in power have just turned a blind eye/let it exist.
For those people who have never seen/heard of outlook, check the links below to see the top half of the main track plus the large drop that's built to the side of the track that joins on part way down. Sorry, would only let me embed one of the links but make sure to check out both as they show different sections of the track. A serious amount of time and effort has been put into the track by some very dedicated builders which has produced some very impressive results. Definitely a one of a kind location with nothing else like it in at least south east Queensland. For anyone who reads [R]evo, it was featured a few issues back for the High Summer photo challenge so it's a well established venue within the mountain bike community.
[video=youtube;qpeuCjvRD9s]http://www.youtube.com/watch?v=qpeuCjvRD9s[/video]
http://vimeo.com/28225440