These two papers shed some light on the challenges faced at North Heads.
From the abstracts ..
The use of Population Viability Indices in making long-sighted urban conservation decisions.
banks2004_AustZool Pop viability analysis
Although remarkably adaptable in its reproductive and dietary strategies, this population of long-nosed bandicoots is likely to follow other urban bandicoot populations toward extinction unless there is active management to reduce the high rate of mortality from motor vehicles and introduced predators.
Scott et al 99 Ecology and pop biology of P.nasuta at nth head