"At the time the report was released, the FSFE questioned why Accenture was commissioned to co-author a report assessing the use of Microsoft software, when the consultancy runs a joint venture with Microsoft called Avanade, which helps businesses implement Microsoft technologies. For its part, Accenture said it has an "independent view of the technology landscape".
"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."
Everything else that is written there points towards it making no sense to switch back to Windows.