"f what you claim is correct, that is frankly utterly staggering."
I've seen the time-line on a Munich doc but can't find it at the moment but from memory the bulk of the desktop moves took place rather recently (~3 years ?)
Yes it's on the document :
http://www.muenchen.de/rathaus/dms/Home/Stadtverwaltung/Direktorium/Strategische-IT-Projekte/LiMux/Dokumente/Praesentation_LiMux_engl_web.pdf page 6
Looks like they spent 2 years getting people onto OO, then 2 years pilots of the linux system (1), then roll-out from 2011.
(1)Until the end of 2008, each of the city's departments will have a "LiMux germ cell". These are groups of 30-50 workstations that will be migrated to the LiMux client. Even in departments that are sceptical towards the migration, this helps the IT staff to become familiar with the software. This approach also allows the LiMux project team to learn about the specific technical requirements of each department, and address them before the full-scale roll-out of the software.