I can't help you with the documentation/references but you may be slightly confusing BRNAV and PRNAV (see your first post).
BRNAV is the capability to navigate to virtual waypoints (not navaids, or navaid referenced; e.g. ORTAC is just a waypoint in space, defined by lat/long) to RNP5 accuracy i.e. be within 5nm of track 95% of the time. This requirement is met by INS (in big jets) or with an IFR GPS (in everything smaller). You also need to have an approved installation which means a TSO GPS and a CDI mounted within a specific primary pilot viewing angle.
AIUI, a BRNAV installation allows you to fly in BRNAV airspace (FL095+ generally; this level has recently been reduced in the UK to all CAS) and allows you to fly "RNAV" SIDs/STARs
if the entire procedure can be loaded in one piece from the GPS database.
Getting a BRNAV approved GPS installation is easy. I think the paperwork is a few hundred quid under EASA.
PRNAV is a different thing. It is basically equivalent to RNP1 but there are additional certification requirements for both the aircraft and the crew. The paperwork is also
today an EASA Major Mod and costs 4 figures.
In practice, an IFR GPS meets the RNP accuracy requirements with a huge margin, but avionics reality has never got in the way of aviation regulation which is firstly a job creation scheme
You also do not, in practice, fly SID/STAR procedures using raw data. You use a GPS. Most people also use a GPS for NDB/VOR nonprecision approaches. Only an ILS is flown using the ILS receiver.
For private flight, there are no regs which stipulate what equipment is
used in each stage of flight.
For commercial flight, the AOC will include a manual which specifies what you do and how, etc. In general, one is allowed to fly NP procedures with a GPS (or INS) but the underlying navaids need to be functioning (not notamed INOP) and tuned in.
There is a real issue with an increasing number of airports whose published SIDs/STARs are all PRNAV. However most (all?) of them give you the option to declare this to ATC and then you get vectors or some other procedure. Most aircraft in the world are not PRNAV and probably never will be. But RNAV capability is simply assumed by ATC everywhere.