[trackflak]

In OpenTTD, each player controls a rival transport firm and you compete against each other on the same map. AFAIK you can also arrange a buyout of your rival, similar to Railroads.

In OpenRTC, each player gets full control over managing the same park from a shared pool of funds. Mayhem may ensure if you set your game to public and don't configure permissions carefully.

In my mind, such an OpenSC2K's multiplayer would work like the latter. Each player managing the same city. Though if they removed game engine restrictions, it would be nifty if each player could manage his own city on one big shared map, similar to OpenRTC.