This is all part of their established mobilization plan. Yes, unlike us, they have had a national mobilization plan for decades.
Critical infrastructure like communications centres, bridges, airports, seaports etc can all be nationalized for defence purposes pretty quickly.
They also used to be able to mobilize a million troops within a week. Not sure how they're doing with that these days, but most people in Norway, over the age of 40 or so, will have been brought up during the Cold War era contingency planning culture.