ADS-B not used in major terminal areas due to a 5NM separation requirement - 3NM is used in terminals which SSR and multilateration systems (SYD Only) can provide (Tasmanian multilat is 5NM system). Primary radar only used around capital cities to guard airspace boundaries. If DS had asked an en-route sector controller they would have been able to see his ADS-B provided there was a nearby receiver - current ones are designed to cover airspace above FL290 but show all ADS-B within range.