I wrote an article a while back about how to run a transparent Software Update server:

http://www.318.com/2011/11/building-a-mac-and-ios-app-store-software-update-service/

I think I'll try it out (it's been a while!) and see how much I can download using my old script. Somewhere there are a few machines which had already downloaded everything - if I can remember where, I can ask the people who have them for a copy of those downloads...