They did use Havok physics, but idk what else... I did like the F.E.A.R. engine but their soft shadowing looked really crappy, and booged down the game.
Just for those who don't know anything about game engines, the RenderWare Engine is used it the Grand Theft Auto series, X-Ray Engine is used in the upcoming S.T.A.L.K.E.R.: Shadow of Chernobyl game, Lithtech's Jupiter EX is used in F.E.A.R. and the rest is pretty self-explanatory