The city is too old.. they don't even have all the schematics for all the gas lines and other pipes and wires laid over the centuries. Digging in Chicago is very dangerous and restricted. It will be interesting to learn how they deploy this if it happens.
As for likelihood this goes through, I can't see this ever happening. It's very corrupt, city employees don't want to work too hard, it's running on borrowed time.
Oh, I'm in Austin now. :) Can't say I care to return to the Windy City but this would certainly help pull in migrants other than native midwesterners.