From #openttdcoop wiki
This is a place where established #openttdcoop players can show their skills at planning, designing, and building in a fresh and clean environment.
The Pro Zone was conceived as a way to help bridge the gap between members and non-members. Rules for playing on the Pro Zone are the same as for the Public Server. You can expect the plans to be a bit more complex and intricate, or to have special themes.
Anyone who is perceived to be a good Coop Player can be scouted to join this server.
We hope the to Pro Zone will become a thriving part of our community.
Since November 2012 the ProZone is open to public, being the place where games get from complex to disgustingly complex state. All players are required to be in the irc channel #openttdcoop.pro where they obtain their password.
You can find the archive of completed games at the ProZone:Archive.