Game runs just fine without connecting to the server.
SimCity can be played offline, a modder named UKAzzer has revealed on YouTube. Not only that but he's discovered that it's possible to edit highways which connect cities together outside of the city boundaries.
"So with a little bit of package editing within SimCity, and a little playing about in the code, it's possible to enable debug mode," wrote the modder. "I linked the activation to the "Help Center" button in the main menu for ease. Most debug features are disabled without having an actual developer's build (they have terraforming tools etc. available in the full developer build!), but a few things do still work - including editing the main highways.
"Not only that - but you can edit the highways ANYWHERE - even outside of your city boundary... and even if you quit the game and log back in later, it's all saved safely on the server.
"This shows that highway editing will be easily possible, AND that editing outside of the artificially small city boundaries should be very viable too."
Regarding playing offline, UKAzzer added: "Other things I have modded out with a quick change: Unlimited time to remain disconnected (won't get booted at 20 minutes, can now be disconnected "forever")."
You will, however, need to reconnect to the server in order to save.
He's also fixed the population count so it shows the real figure.
You can see the fruits of UKAzzer's efforts in the video below.
EA and Maxis has been adamant that SimCity must be always connected because essential processing takes place on the game's servers. This mod seems to indicate that this claim isn't true, backing up reports from a Maxis source earlier this week.