You probably saw this article already http://www.zdnet.com/article/huge-savings-prompt-italian-city-to-dump-openof...
First of all I think it makes no sense to talk about ownership when you talk about services. You can say total cost of operations. But that is different than when you own something.
My second question (I hope some Italian speakers can clarify): Do they really compare the costs for running Microsoft Office and Apache OpenOffice in parallel with just running Microsoft Office??
Regards, Matthias