I think the level is actually at/above FL100, but the answer would depend on the reason for asking.
BRNAV is not equivalent to RNAV. BRNAV is a specific equipment performance and certification. RNAV is merely the ability to navigate to virtual waypoints directly, and any GPS with a DCT function delivers that.
There is also the practical aspect. Airways ATC assume everybody has RNAV capability, regardless of FL100 or below, and will happily send you to a VOR 200nm away, treating it as just another waypoint.
In some areas e.g. Greece, ATC expect you to have RNAV capability even on VFR flights and expect reports at specified airways intersections. Nice
Another bit is RNAV STARs - these obviously go below FL100 but you need PRNAV to fly those, and PRNAV is yet another equipment performance, functionality (this one is not defined
AFAIK but an auto slewing course pointer i.e. an EHSI is one possibility) and certification level..... probably the majority of European planes with IFR GPS installations cannot legally fly these procedures (usually there is the "advise ATC of you can't" option). This one is a bit of a worry, if large chunks of airspace become "mandatory PRNAV". Anybody with GPS-based RNAV capability can fly there
practically (and easily to the required accuracy) but not legally.