It's a pretty basic PvP UI using nothing but OmniCC. You can customize this using everything blizz gave to you. He unlocked the frames (Player, Target, and Focus) and moved them to the spots they're at now. He turned on "show party as raid" frames and those are the thick color coated party frames you see above his player portrait. The things on the right showing cast bars are just Blizzard's default arena1-3. To be honest, I suggest getting Grid to replace it.