Last Month the Japanese try to retrive this mod a little bit more. They played in the at 2pm CET. At the moment the gametracker,com Server Monitorring is off. Hope soon they turn it on. The ranking seems to work.
Its kinda random. Unless some gathering is announced on the site, people join the server at any given time. I've noticed some evening activity in EST American time from 7pm - 2 am which in France for you is 1am - 8am. But that doesn't necessarily mean that people only play at those times. If someone is in the server, people will join.