> License savings. Great.That and other related admin such as keeping all installations in check to make sure you are within your license terms. Have you budgeted properly for the time of experienced people to fill out paper work and the potential disruption of everyone else if a full audit is requested (the license agreement says that can call one of those when-ever they like IIRC).
Sometimes using Office most definitely is the right answer (the "compatibility with our suppliers/clients" issue often can't not be ignored for a start) but when it isn't the correct answer pure licensing costs are not always the only reason.
> What was the cost of: Re-imaging those 120,000 desktops?
The costs of this change per desktop will be similar to an upgrade of Office.
If they are upgrading from an older version of office that is no longer supported and the choice is between newer office and OO/LO then this is moot. There may be a bit of extra time at the start of the project as those running it get familiar with OO/LO's installation foibles, but considered per desktop this is not going to be high.
In fact installing OO as a new package may be more risk free as it can co-exist with their current version of Office, so they have an easy fallback/rollback or slow transition option.
> Re-training the (I assume) 100,000+ users?
The differences are not that significant. If they are moving from a relatively old version of office then the retraining for the newest Office variant could easily be more significant due to the UI changes over recent years.
If they have any custom training materials then there will be a cost for updating these, but then there will be for Office too.
> And what are the support costs?
Again, I doubt these will be significantly different. There might be a little more effort needed here due to people being familiar with Office due to the copy they run at home or used at a previous employer, but again there is the "which office version" difference which may make this a moot point. If people using something at home is one of your considerations and you are relying on it to reduce your support costs then OO/LO makes sense as everyone can have an install of OO/LO at home legally for no cost.