Well, there's this in the Forward on p7 of the White Paper, repeated in the main body:
Not much room for doubt there, I would have thought.
Doubtless there are different levels of activity and not all will be in GBR HQ, but the strategic bit will surely?
No doubt it will impact the DfT, RDG and current TOC teams too.
I'd expect GBR (HQ) to manage the timetable cycle and publish the GBTT.
Not sure about the WTT, it might stay with the Regions/Routes , which are bound to be somewhat separate.
Speculation of course.

It quite clearly says NR will be "absorbed" into GBR.