Technically it is possible, nothing in game development is "impossible" within certain limits.
They have alot of other issues with persistent terrian updating and database stuff that it seams is affecting the entire game engine.
http://vimeo.com/4304024It's definately doable with this engine so it must be something they've modified for thier purposes that has made it non functional. So basically it's not the engine, it's the developers and the poor database infrastructure.
Honestly though a premade map for YO and MMO ( instead of procedural ) and no real rivers is a deal breaker, imho.