Surprise attack gardening

A trend that seems to around at the moment is "guerilla gardening" which was started in New York in the 1970's, but is currently undergoing a revival. This random joyful expression changes public spaces and involves groups of people getting together to create gardens quickly and in strange and unusual urban spaces. The beauty of this seems to be that completely unwanted and unloved spaces are used and with rent and space pressure a little garden could go a long way. There is a story about this in the current YEN magazine and a website tropolism has a decidated section to pop-up gardens in New York City. I wonder however are there any Sydney Guerilla Gardeners out there?