[Jayschwa]

I believe some tech from id Tech 5 was back-ported into it. Wikipedia says it also has support for 3D [head-mounted] displays.

[phoboslab]

Yep. John Carmack stated that the BFG edition is actually Doom 3 in the Rage "framework". E.g. Rage's network layer and (probably?) all the behind the scenes stuff like input and file management, boilerplate for different GPUs etc.