It seems a major factor was that the SFIS controller (sitting comfy up in Brisbane Centre) had no positional information on the C208 as there is no surveillance below 1,500 feet. From the report:
Airservices Australia conducted a risk assessment and rated the initial risk as moderate. However, its pre-implementation risk treatment did not reduce the risk any further. Residual risks associated with the surveillance coverage limitations were formally accepted and the SFIS was implemented with the risks unaddressed. These limitations meant the Caravan’s positional information was not displayed on the SFIS controller’s console screen until it reached an altitude of about 1,500 feet, which occurred about 100 seconds after take-off was commenced.
So how could the S in SFIS ever have been taken seriously?
Don't worry though, ADSB ground station is coming...