After some quick googling Research into this does suggest brainwave patterns may well be unique to each individual. But they are still just electrical signals as far as the machine is concerned, and as such could easily be adjusted via filter or spoofed to whatever recording method is used. If it looks likely G.O.D. was about making brain pattern library, I'm sure the community could easily adept to foil it.
But what then if a user didnt use his brain waves to form his persona ( and no Im not talking about the dimmer bulb quality).
Say a physical adept AR decker. He has his goggles with image link, earphones with sound link and AR gloves - no trodes. In this case his brain waves arent near his deck, yet if he is able to form a Persona in AR (which I belive he is) thrn that Persona is formed without ant direct input from hus wetware.
I know this might be overthinking it all, but I find it an interesting subject.