This install used to have all telemetry turned on, but I turned it off a month or so ago.
I suspected a full reset of my setting, but apart from Telemetry collection being back on, Windows Update via peer to peer and the above firewall rules added, no other settings were reset as a result of the update.
Windows Update would probably also be reset, but as it has always been on I am not able to tell.
So far, Microsoft has not automatically delivered major updates like the 1511 release to Enterprise installs and so I did most other installs manually months ago by downloading a new (on premise) image from the MS Partner Network (even had to input a new serial as well and so I am really surprised that this happened).
After the update, the install is still activated and no further actions required.
I did read that they planned to do major updates also for Enterprise Editions not connected to WSUS or managed by Control Center, and so it seems to have gone live.
The Enterprise (N) LTSB (Long Term Servicing Branch) is still July 2015 which is also the current downloadable image and so I'll have to wait for Redstone 1 to see if MS will upgrade it (my hunch is no since it is meant for mission critical installs and does not get feature updates at all).
FYI: The N version does not include Windows Media-related technology and LTSB was advertised a 'The programs you install today are guaranteed to work until 2025', which means it only gets security patches.