The city government of Munich, Germany switched from Windows to Linux in 2004 but appears to be on verge of returning to the Borg. Tech Republic gives some background:
At the time Munich began the move to LiMux in 2004 it was one of the largest organizations to reject Windows, and Microsoft took the city's leaving so seriously that then CEO Steve Ballmer flew to Munich to meet the mayor. More recently, Microsoft last year moved its German company headquarters to Munich.
Microsoft's tactics seem to have paid off, as Munich's politicos are "poised" to vote next week for a move to Windows 10. It's ironic that as Linux has improved over the last ten years, Microsoft has gotten worse, and the most compelling argument for a business or government to use it is still "everyone else does." Meanwhile, ordinary consumers overwhelmingly reside in Apple-or-Google-land, because they are all using "devices."