EA revealed that the upcoming Medal of Honor game will use two different game engines. The game developers decided to use a heavily-modified Unreal Engine 3 for the single-player part, while the multi-player mode will use DICE's Frostbite engine.
A tweet from "#MOH" (EA Los Angeles), and another from EA Community Manager @matthewpruitt confirm that the single-player portion of the game will use a "heavily-modified Unreal 3 engine."
Another tweet from DICE Frostbite developer "@repi" let more information slip:
@repi: Guess it is out today: EALA uses a heavily-modified Unreal Engine 3 for Medal of Honor SP and we, DICE, use Frostbite for the MP portion
This was quickly followed by another confirmation from @matthewpruitt:
@matthewpruitt: I guess the cat's out of the bag. Medal of Honor's multiplayer will be using the Frostbite engine.