Vienna (German: Wien) tried it too between 2005 and 2009:
There is a nice article in the free Software Magazine trying to reason, why it failed:
http://freesoftwaremagazine.com/articles/vienna_failed_to_migrate_to_linux_why/
Tony Mobily says they simply should have gone for Ubuntu or CentOS as a municipality cannot (as in: it was a “mixture of madness, boldness and sadistic intentions; or, maybe, just lack of experience”) maintain its own Linux distribution. And of course it was also the fault of Microsoft’s pressure. (Aaand we reached this topic again: Microsoft “goes Open Source” (= acquired GitHub) .)