Depends whether the BN2P has suitable instruments for the RHS pilot as per the EASA regulations. It is not possible to operate as multi crew if the RHS pilot has to look across to the instruments on the LHS to fly approaches, I seem to recall that the regulations require any instruments to be within 6 degrees of each pilots forward vision to be able to classify the aircraft as suitable equipped for multi pilot operations.
The next question is who is signing the technical log, if it is the line training captain then you log PICUS, if it is you then you can log PIC. That said, it would be normal for the line training captain to be commander of the aircraft and therefore you could not log PIC; ORO.FC.105 refers.