I don't know about it all being the brinkmanship thing.
Putin/Gazprom are trying to engineer a pro Russian government in the Ukraines March elections. In their jack boot type minds what better way to get the electorate to reject a pro Western goverment than by having the people freeze for a couple of months in the Winter.
And Gazprom will cut off the supplies if it sees fit - it did the same to Belarus a couple of years ago. I don't know how many froze to death but it must have been in the thousands. Needless to say Belarus got a good deal this year, but then it did hand over much of its pipeline network to Gazprom.