Specifically mentioned are three mining companies:
-- BitRiver -- Minery -- Cryptoreactor
Cheap electricity (3.4 US cents / kilowatt-hour), cold weather.
The article mentions that most machines there are owned by Russians and Americans.
As I know Hashmart is in Siberia too and weather is the reason of this location choose. What a pity they did not put it into the list of three. It has to be among them.