Re: (km123) This is about Government POLICY overriding a PREFERENCE for Windows
That German FO switch was more about politics (as there was a power shift in Germany) than practicalities from what I understand, especially given this from the story you link:
"All that despite McKinsey confirming in 2009 that the German Foreign Office had splurged less cash on its individual IT workspaces then any other federal authority in the country while running a Linux desktop shop."
Although understanding anything a government does is difficult at the best of times.
We can cite stories back and forth, but that doesn't change anything. Whilst people use MS only formats (e.g. Office Open XML*) and MS only code (i.e. anything that only runs on Windows); then MS have you by the balls. If organisations spec open standards and portability, they have a much better bargaining position and can keep their costs down (even if they ultimately remain on Windows).
*Before some Windtard chimes in, yes; I do know that in theory Office Open XML is an ISO standard and in theory an open standard. The actuality of that is, however, rather different (e.g. the "openness" only applies to a specific version of ooxml). The only true open standards IMO are those spec'd by OASIS (e.g. odf).