Wow, I am really impressed! They seem to really use an emulator (other techniques would require much more work) as hinted here: http://www.neogaf.com/forum/showpost.php?p=168068069&postcount=1780
I don't know how but I guess we get a false image on emulation because we mostly only know homebrew emulators. If IBM did a ppc-x64-emulator it seems it can be leagues better because they know better than no one how the chip works. I guess the load is pretty heavy on the Xbone and let's see how demanding games will perform with this solution.
PS3 emulation on PS4 is a different story - the PS3 has too many cores you would have to emulate. Even by 1:1 matching the cores it wouldn't be enough as the PS3 has 7 in total but only 6 available for gaming purposes, not to mention that you have the PPU as ppc and the SPUs with cell with their own dedicated isa which is way more similar to a GPU than a CPU. There won't be enough power.
