yeah, much like the Source Engine is a heavily modified version of the Quake Engine. I've heard they are using the Unreal engine so, sadly, it's going to be a brown FPS with space marines because that's hard coded.
File formats are interchangeable, the engine is most likely the same, it was gamebryo(which is a rendering engine) that they replaced with their own stuff.
Kind of like how people think games made in unreal engine always have bulky space marine characters and gray plastic looking environments covered in glowy bits because the engine works that way.
Here's a fun thread from the official forums It irritates me to no end when I see people posting complaints about the engine on the bethsoft forums, kotaku, etc. Like, I don't understand how these people know the name of the game's engine when they clearly have no idea what an engine does. That age-old trend of blaming the…
It is likely though that they got help bringing their own new graphics engine up to date with the help of id. Bethesdas engine (not the gamebryo graphics part) has always been very different in structure from the way you do things in ID.
^ QFT, a friend of mine complained that CE3 engine is very good for games with Mecha in them, and that UDK makes bulky rough skinned marines look cool, while if you want for soft delicate skins like that of a sexy female warrior, then you need to use the Crystal Engine (FF13) and that no one engine can make everything look…