That's a cool system, but if you dig 17 feet deep here you're going to hit ocean. Maybe we can use 'bike trees' instead. We do have storage lockers available at the metrorail stations. Cost is pretty reasonable, but I ride the metro only once in a while so it's not worth it for me.
However, I will admit that I'm considering using a hardened steel chain in conjunction with my Ulock, despite the huge weight penalty. It's kind of crazy that my locks alone would weigh more than a bike used in the Tour de France.