From experience I know that most people don't care about the OS, they probably just need a browser, Thunderbird and LibreOffice. So I don't understand the decision. They are corrupt or very stupid.
They most likely have custom software that was build for their "public administration", and it only runs on Windows. Plus, I guess, non-working printer drivers and not being able to exchange .doc/.xls documents with other offices that only use MS Word.