It's not a new office; it's existed from 2015 or even earlier. They've just decorated it for E3, I suppose (I saw what was presumably the same image in another official source).
Also, this isn't a GWENT thread, so moving to Community.
They probably handle stuff like localization, PR, logistics etc for their respective areas, afaik the only game development ones are in Warsaw, Cracow and Wrocław.