At the risk of sounding ignorant, but given that the assessment for RPEQ is now able to be handled by IEAust, and that the IEAust registration (i.e. CPEng and registration on the NERB) can be used as an equivalent to an RPEQ assessment, why would the BPEQ be in discussion with the other states and territories regarding a national system?
That said, I've seen different requirements in different places regarding such things. As an example, NT requires practitioners in certain disciplines to be registered (notably electrical isn't one of them) in order to provide certification of design works.
I would suspect that if IEAust was more enthusiastic about chasing errant members then QLD wouldn't have needed to have gone down such a path, but its rather hard to say.
I must admit I'm not keen to have to shell out two sets of fees for registration, and I'm certainly not keen on the liability contraints imposed by the BPEQ, but at the same time I can see the requirement for 'keeping the cowboys out' as it were.
I do recall, however, being informed by an employer (QLD based) that in QLD, if an event happened (obscure failure mode, one in a lifetime occurence that adversely affected a design) then it should have been foreseen by the engineer, and that this was then a case for negligence. I was also informed that this consideration didn't occur anywhere else in Australia, though they were considering it. Such things are concerning given the presence of a state board that prosecutes registered engineers.