It seems as if the failed city-building MMO has become a fairly regular offline city-building series. Cities XL 2012 will be arriving in October, and expands on the previous offering considerably. Focus explain: "Cities XL 2012 allows players to become real urban planners, balancing economic & energy developments of their cities while managing transportation, housing, social services and recreational activities. Content is key to the new game, as Cities XL 2012 offers a staggering number of unique structures with over 1,000 in total."
The game also now, apparently, open to modding, with a bunch of mod tools included in the 2012 release. A wise move, I suspect.