BRNAV is for area navigation not terminal navigation. Basically below FL100 your not meant to use it (but we all do). .
I don't understand that.
BRNAV is a certain level of lateral accuracy. It is available to you whenever you are flying according to some form of track guidance.
Are you saying there are passenger or cargo jets flying in Europe which fly using the FMS (i.e. INS with DME/DME or GPS corrections) when enroute, and after they cross the terminating waypoint of the enroute section, and if flying a
non RNAV STAR, they track VORs until the IAF?
If so, who is doing that and what in?
If that is really common then I can see PRNAV is a huge spanner in the works because they will all have to rip out most of their panel.
Any half decent GA IFR tourer can auto-fly (perhaps with the pilot hand turning the course pointer, if he has a mechanical HSI and doesn't have GPSS) the whole enroute and terminal path with ~ 1/4nm lateral accuracy all the way to the IAF and then intercept and track the ILS to 200ft AGL.
SIDS and STARS will all reference a radio aid if you do a PRNAV SID and STAR the points can just be abstract points in space with no reference to a radio aid
Only
non RNAV sids/stars reference navaids for the entire track to the IAF. RNAV ones don't (for the most part of the track distance) and same for PRNAV ones.