City of Munich Saved Taxpayers A Lot Of Money With Switch To Desktop Linux
(computerworlduk.com)
And other cities (at least German cities I guess) adopting the same system wouldn't have to spend the 2.5M€ they used for custimising the software, supposing that the needed customisations would be similar...

It's not really 15 million, is it ? A quick read of the article seems to indicate that the LiMux project itself cost 13.78 million (11.7 dev + 2.08 opt and test).
Re-reading it I get that 11.7 is the total cost of the project, but actually I can't understand which numbers should be compared with which... I'll change the title anyway!