There is quite a lot of crossover between the exploration part of UE and geocaching, although geocaching caches generally don't involve anything that could be called trespassing... generally

Some of the high terrain difficulty caches in NSW are definitely expos in themselves.
The easy ones are probably no challenge to the visitors of this site, but I find that keeping an eye open for them makes the urban environment more interesting... you never know what someone has hidden out there.
There's a good Australian website for geocaching and I thought I'd post a link. PM me in case anyone wants some recommendations for good high difficulty caches to try and get to.
http://geocaching.com.au/