How does an organization upgrade to Mountain Lion? Is it possible to create a generic Apple ID and purchase multiple copies from the Mac App Store? Are there any other available methods? Once one Mac is upgraded, can a DVD be created and used to upgrade the rest? How many license are needed? Individual upgrades seem to be good for 5 installs, however I suspect that does not hold true for organizations.
My experience went something like this, not sure how typical it is:
Apple Rep, was contacted. There is no volume discount for less than 20 licenses, but I think we did pay with a PO. We got an encrypted PDF with some keys. Everybody that needs to upgrade can create an individual Apple ID using their organization e-mail address (select the 'None' payment option), click on 'Redeem', enter one of the keys and download and install Mountain Lion.
I hope we never need to transfer a license between Apple IDs.
The general advice is that Apple has sales channels (within the retail stores as well as without) to assist organizations understand the various programs and licensing terms. Additionally, organizations typically get tools to assist with license management, support and deployment.
If you don't have a sales contact yet, you could start with this somewhat dated, but very nice white paper on the issues for deploying OS X in a large scale setting:
There are more up-to-date presentations for the App Store, but I haven't seen them published on the web.