As many suffered through SimCity's often unplayable launch due to its absence of an offline mode, EA claimed that its servers were necessary to the game's performance, regardless of its social features. "We offload a significant amount of the calculations to our servers so that the computations are off the local PCs and are moved into the cloud," Maxis general manager Lucy Bradshaw explained to Polygon. "It wouldn't be possible to make the game offline without a significant amount of engineering work by our team."
However, an anonymous source recently told Rock, Paper, Shotgun that this explanation is bunk. "The servers are not handling any of the computation done to simulate the city you are playing," the source - which RPS assured is verified - explained. "They are still acting as servers, doing some amount of computation to route messages of various types between both players and cities. As well, they're doing cloud storage of save games, interfacing with Origin, and all of that. But for the game itself? No, they're not doing anything."
The source further noted that the servers take several minutes to transfer data around, suggesting that it couldn't be influencing the game's performance on the fly.
There's a more technical explanation on the Rock, Paper, Shotgun report, but ultimately, the source claimed "It wouldn't take very much engineering to give you a limited single-player game without all the nifty region stuff."
Already Kotaku and Markus "Notch" Persson have realised that the game can be played for several minutes after being disconnected from the internet. Either the game is haunted, or something else is afoot.
We've reached out to EA to hopefully get a response on what in blue blazes is going on. We'll update if we hear back.