Rumor: "It wouldn’t take very much engineering" to build an offline mode for SimCity

We've been told by Maxis that despite what everyone seems to want, it would not in any way be easy to take SimCity offline. They've said that many of the computations the game makes are done server-side, and so "it wouldn't be possible to make the game offline without a significant amount of engineering work by our team." But that stance may not reflect reality, according to a RockPaperShotgun source.

This source asserts that no computations involved in simulating your particular city, in fact, take place in the servers. The servers do have to interpret data you send out into the world, the source says, but your own PC does all the legwork required to run your city. So what does that matter? Well, here's the source's conclusion:

“It wouldn’t take very much engineering to give you a limited single-player game without all the nifty region stuff.”

What do you guys think? Is Maxis just trying to build a wall around its DRM practices or is this guy full of it?