The potential upside like you mention would be more licenses at lower cost. Whether that was a bottleneck depends on the organization in question. Either way I don't think it's possible to make any conclusions without research.
However, staff productivity is not generally a major concern in local government offices, as far as I can tell. Maybe Munich is different, but I doubt it...
That doesn't make any sense. What is inherent about closed-source that makes it hard to use and what is inherent about open-source that makes it easy to use?
I think the important phrase here is switching away. That implies there's been a change, which brings increased training (either formal or learn-as-you-go) to learn the new system. If they need Word for their job and now they have OpenOffice, that's not a productivity gain, that's a loss at least until they get up and running (and then it's an ongoing loss every time they need to convert a docx with custom formatting that OpenOffice doesn't understand.)
I agree on OO. The risk in my eyes here is that OSS (desktop) software is almost invariably less productive than proprietary software for some reason. Switching that way can make sense if you save a lot on licenses, administration etc., but if you have to pay once for a switch AND then pay continuously by using less productive software you are taking a much higher risk. It may give a warm fluffy feeling to be using open standards, but the problem is that the only standard that exists is a de-facto proprietary standard set by Microsoft. It may be noble to try to change that, but I certainly wouldn't want to spend tax money being the first major city to do so.
Well while we don't need to state reasons, there is also the risk that all proprietary software is less productive for some reason.
How do both of them weight?
The one thing that is certain is that administrative costs of prorpietary software do reduce the softwre availability, as spodek said.
Only from simple empirical studies of a few software packages (OO vs MS Office, Gimp vs PS, Eclipse vs IDEA, Blender vs. many) I think it's fairly obvious that the "normal" open source model doesn't match the megacorp development model for complex desktop software. My best guess at the reason is that 1) Ivory Tower is better than committee design for user interfaces 2) you need a LOT of expensive non dev resources such as designers and focus groups which just don't seem to materialize for the open source projects like they do when Adobe or Microsoft waves a pay check.
I think there may be lots to save in administration, servers etc when moving to Linux, but 2014 isn't the year of desktop Linux, far from it. You really can't motivate not buying office for a few bucks per month and expect to save money.
You CAN probably save a ton by ditching exchange/SQL server and so on, where there are plenty of good alternatives. But Ubuntu/OpenOffice instead of Win/Office? I doubt it, given reasonably low volume license costs.
(Average gross salary in Germany was €3,391 in 3Q2013 so the cost of employing someone would be higher than that.)
http://en.wikipedia.org/wiki/Usage_share_of_operating_system...
Nobody cites Windows or Office as an impediment to growth. It is very unlikely that the Windows Web client share decline has ever hit a "productivity" speed bump.
Another way to look at it is that mobility turned out to be much more highly valued than Office or Windows compatibility.
E-mail, basic document forms and internal applications are the major use-cases for that type of scenario.
Taking your example of Gimp, I expect institutional adoption of free software would result in some people having it who didn't have Photoshop at all before. They can now become more productive and take less of other people's time.