The paper describing the splits defined breviceps (the Sugar Glider) as having a distribution reaching south to Eden in NSW (c.50km north of Mallacoota), which would make all of Victoria solely within notatus (Krefft's Glider) range. The authors stated that there is no evidence of distributional overlap between the two species, however they also (understandably) made a point of noting that given the pretty close proximity of samples at the Victoria/NSW border area further study was needed to confirm whether they did or did not overlap in reality.
@Chlidonias yes, I noticed that the original paper suggests breviceps do not make it into Victoria. Interestingly, the HMW illustrated checklist states that breviceps extends into eastern Victoria, which made me wonder if there was any additional information floating around... Given the split is based on just the one paper, I find it hard to be confident in such hard range boundaries where there is no obvious geographical feature to encourage speciation.