CASA’s interpretation is in the “Advisory Circular”.
Yes indeed it is, and clearly states -
8.2.1 The operator of a model aircraft weighing over 100 grams is required to obtain
permission before flying a model above 400 ft AGL within controlled airspace or within 3
nautical miles of an aerodrome. While this rule means that a model aircraft may be flown
above 400 ft AGL clear of these areas, there are advantages in seeking approval for a
permanent model aircraft operating area.
While this rule means that a model aircraft may be flown
above 400 ft AGL clear of these areas...End of....no proviso, no 'subject to approval'...none, and in fact rather cut and dry is "While this rule means" a bit like 'Shall' rather than 'Should'
Still and all a humble little RC pilot would never have the resources to defend him/herself against a body such as CASA....we know what they're like....
It does suggest though that model flight below 400ft AGL and within 3 Nm is allowable without permission