The Department was anti - SBAS most likely because someones career was heavily invested in GBAS. CASA probably couldn't have cared less. The drivers for aviation regulation in Australia are plainly the career prospects of the regulators.
Here is a prediction: Avmed has jumped on the sleep apnoea bandwagon which is making millions for doctors. The AMA (american) has just redefined "high blood pressure" ten points lower then the current definition. Watch CASA Avmed grab that new definition with both hands and ram it down our throats at more expense.