Crossing ht at TOLLGATE
The crossing ht. at tollgate is a minimum height, not maximum height, to insure that from that point onwards the aircraft will be able to continue with engine failure and clear the high terrain ahead. The restriction on how high the aircraft can cross tollgate is CLOUD BASE as the departure is a visual departure until reaching tollgate.
The "don't sink" aural call out occurs if the aircraft begins to descend after takeoff, before it has climbed above 700ft agl. Cloud must have been shelving down on takeoff path to below 700ft agl. Requiring the pilot to descend prior to reaching 700ft agl.
If the minimum height at TOLLGATE could not be attained due to low could, the aircraft would be required to fly a visual maneuver in the valley and return to land.
RNP-AR approvals can take over two years for the regulators to approve, in the meantime operators are left with a, less than ideal, departure from Queenstown.