hang on, once again i think that whole business about saving is true
the game requires always-online. the only way to play alone is by (basically) blocking people/making your city private. it's not really a "single-player" mode, just a play-alone option on an online multi-player game.
think Diablo III, you could play alone but you were still playing online and couldn't save your progress, no?
i'm just not sure. :/
I really want to play it though. Regardless of the potential restrictions, SimCity is still SimCity.