I have several workstations on a Windows domain set to share Windows 10 updates in hopes that each workstation doesn't have to wastefully download its updates directly from Microsoft:
This seems to have been working in previous updates, but there doesn't seem to be any share-utilization regarding the Windows 10 1511 update. Each workstation seems to be downloading 1511 independently (directly from Microsoft).
I've heard this update is larger than 4GB, so you can certainly see how extremely wasteful this issues is.
Some of our workstations have this update successfully installed, so I don't understand why the remaining computers aren't downloading the update from these already-updated-computers on the local LAN.