I'm pretty sure they're just doing round robin DNS, as I had one rig on one of the true European servers and other rigs on the Japanese or whatever they are... So it depends, which you get on the first dns resolution.
It's happening on the eth-hub aswell, I already posted multiple times about this, I tweeted MPH, and zero response until now. I would like to keep my rigs on MPH, but i've been testing etherminer the last couple days and will do rerun of nanopool as the support on MPH on this issue has been non-existant.