Hi all,
I hate to be the bearer of bad news, but there's actually nothing inside either Karabor or Shattrath now that the expansion has gone live; during the BETA there was untextured interior for Karabor (Which I still don't know why it's just been re-'moved'), however there's only the doorways / central crystal left. See below:
Karabor:
Shattrath
On a slightly better note however, I have a sneaky suspicion that the developer playground still exists south of Nagrand after running there today. (Cannot currently access it due to flying restraints, but there was a minimap indication)
Thanks all!