I get the impression that the region system is server side, going by the lag as much as anything, and I've no doubt creating an offline version wouldn't be simple. It's not just a switch. It's probably not even Windows code.
However, it's nothing that couldn't be done better offline. The amount of processing per region is minute, individually it would barely register on a computer. Of course, if you have thousands running at once on the same computer, then it might slow down.
I believe that a large part of the simulation runs server side, however this is only because they deliberately made it that way. Apparently there's some sort of economy going on ... I haven't noticed any thing.
The only parts which actually need to be run on a central server? Leaderboards ... a pointless feature they switched off to save their servers. Fucktards.
I'm sorry I bought this game. I should have checked properly, I thought the reports of the always-on requirement were FUD, and then I forgot about them.