I don't think a lock can be rigged so that someone can open it once you lock it. Here in NYC people leave locks on racks all the time. One of my favorite lock stories is that I used to leave my Kryptonite chain wrapped around a street light. I didn't bring the bike in one day and just happened to glance at the street light where my chain normally is and it was gone. So was the street light, leaving only the 2 foot stump that the pole sits on. I went to complain to the local police department and when they stopped laughing they suggested that I call the utility company.

I called, they told me that, yes, that street light was removed because it was damaged, and they got me in touch with the contractor. The contractor said, yes, there was a lock on the pole and they left it on the nearby bike rack. There was, of course, no nearby bike rack because otherwise I would have been using that rather than a street pole. I never got it back but I get a good story about how someone removed a street light so they could steal my lock.