Assuming PVP zones work like the rest, getting a loading screen while in a zone indicates server overload which momentarily prevents the client receiving zone updates and it throws up the loading screen.
It's been seen throughout the life of the game from time to time in PVE zones so I guess same applies in Cyrodiil too.
If this was near a keep (in PvP) then screens often appear during keep clips or walls being repaired and going back back.
@Turelus - EU PC Megaserver "Don't count on others for help. In the end each of us is in this alone. The survivors are those who know how to look out for themselves."