Anyone who has ever stepped on a Shinkansen can understand that Japan has a way of getting shit done. It may start a bit later than other countries, but when they finally decide to execute (and this is still in planning stages so it might not), it happens surprisingly quickly.
I've watched them totally revamp Shibuya station over the past 10 years in ways that make it utterly unrecognisable to someone who hasn't been here since then, all while never taking down-time. There is another article on the HN front page titled "Why it takes NYC nearly 10 years to install 500 feet of pipes" right now... that's perhaps coloring people's expectations of the possible.