Don't forget Munich saved 10,000,000 Euros doing this[2], and --let's be honest -- doing the same thing with windows computers wouldn't have saved more than maybe a couple years at most.
[1]http://www.wired.co.uk/news/archive/2013-10/01/french-nation...
[2]http://linux.slashdot.org/story/12/11/23/1732222/limux-proje...
That's a big assumption, and one that no doubt helps push the price of the MS solution up considerably.
There's no case study more massaged by those who want certain outcomes than the Munich linux migration. I also believe they were running NT4 when they started this project, so they're definitely the type of organization that is very behind the tech curve.
I don't have a preferred outcome and wish them the best, but there's so much BS and massaging of data here that its all fairly useless to those of us interested in how this really turned out for them. Pardon me if I don't considering slashdot as a reliable and unbiased source regarding TCO of Windows.