BT have published a document - STIN 518 - on their
SINet website, about the NGA2 "Fibre on Demand" and G.fast trial.
I think most of the details about G.fast have already been released elsewhere, although for G.fast, it does mention:
Note: The new version of NTE5 is required i.e. the one WITHOUT the protection device installed.
I'm not sure how "new" the NTE5 referred to is, nor what the protection device is. I've seen the NTE5 on Run IT Direct advertised as being the latest version which doesn't have a 26A surge arrestor, which it says may improve ADSL/VDSL speeds, so perhaps that's it.