Details say it's an enhanced version of UE3, but I don't know which version they built on.
The lighting looks similar in quality to Gears 3, which is probably the prettiest lighting I've seen in a game yet (of course, that game is using Lightmass)
Looks like a recent version of UDK/UE3, but showing more restraint with regards to postfx and grungification(tm) then the average UE3 game.