And their IT department will be manned on 11/01 as well as any other data center in Bavaria that serves customers in whole Germany or other countries
As I said before, service providers will be manned and work on 11/01 in Bavaria or BaWü, because customers in Hamburg, Cologne or Berlin don't care about a single holiday in Bavaria, if their paid services and products don't work. IT departments, service hotlines will work with reduced manpower, but they will work.
Of course it will be manned, but not as much as normal. It would be idiotic if they launch it while most of the developers and it guys are on a free day. There will be only 24/7 people which are maximum 1/10 of the department.