"With the way that the game works, 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. It wouldn't be possible to make the game offline without a significant amount of engineering work by our team." I'm going to point a finger and say that this is clearly untrue, and very easy to disprove just from basic network monitoring ove…
It's clear that the quoted text was a lie from the start. There's nothing you could do in an EC2 instance that I couldn't do on my quad core i7 at many times the speed and a fraction of the cost. Even if you matched users one-for-one with large EC2 instances, you'd be looking at hundreds of thousands of dollars an hour (and that many don't exist).
That said however...
If there's a shared world, then running its simulation server-side makes sense. Not the game minutiae, but global state. Something like weather, simulated stock markets, etc. The environment, basically. That's not to say that SimCity has any of this, because it doesn't.