The essence of BRT is dedicated guideway. BRT stands for Bus Rapid Transit. 'Rapid' is a technical jargon for exclusive right of way.
A BRT that shares right of way with cars is just a bus. Be it double-articulated, double-storied, multi-door boarding, off-board fare collection, significant stations, with 5-minute frequency. It may be a very nice bus. The FTA can call it 'BRT-lite'. Nonsense. Not BRT.
Contrast with Real rapid transit:
'Metro': Grade separated crossings, underground or elevated track (both exclusive).
'Pre-Metro': Grade-separated crossings, exclusive track
Light Rail Train: Time-separated crossings (railroad gates), exclusive track.
Light Rail Tram-Train: Time-separated crossings (intersections), exclusive track.
Nor Rapid Transit:
Light Rail Tram (Streetcar): Time-separated crossings (intersections) dedicated or shared right of way.
Getting away from 'dedicated' right of way, and obtaining exclusive right of way is hard. Demand for right of way for automobiles is constant, and most severe at intersections. The UTA Trax shares left-turn pockets with automobiles, to it's detriment, and to serious detriment of safety. And rare is the 'BRT' that doesn't have a side-running section where it sits behind right-turning cars.
Read the ITDP BRT Standard. When someone tries to sell you BRT, ask what 'grade' you are getting.