The term coworking is known over here (for example, there is a Wikipedia entry in Japanese on the subject: http://www.laveudemallorca.cat/n…), but there is definitely no scene at this point.
More information and pictures on coworking spaces in Tokyo in particular can be found here: http://ameblo.jp/moboff/
Due to space limitations and high rents, there have always been variations of the concept (shared offices, for example) in Japan, especially in bigger cities.
A company called Noboff has recently opened coworking spaces in various places in Tokyo:
I visited their Shinjuku space a few weeks ago: very nice offices.