Would be great to see some articles on their technical approach, I assume they have used techniques to reach those scales based upon the fact the average pair of players are too far away from each other to be visible
It seems hard to general to get your hands on any modding code. Apparently the modding culture doesn't encourage opensource as much as other hacking circles.
Modding seems very 'credit-heavy' and it can be difficult to get credit for your work when a bigger, better team can simply fork your code and call it their own. Then again I don't have any experience in this field so I could be completely off-target.