Not sure if this is still the case at BNE... but in a similar vein I saw that other than Australian passport holders were being allowed through the Australian passport holders line.
I wrote to the Head of Brisbane Customs to ask why... lo and behold I and my airport manager were invited to tea with the Customs gentleman and two others. It boiled down to the fact that they didn't have sufficient funds to employ the requisite staff to police the queues!!!