Irregular aviation movements and ATC

[Arthur T]

There are heaps of special aviation movements around Sydney and even some on the departure/arrival track.

These are the balloons which often attach some advertising material (I saw one at Coogee Beach, right on the departure track) and on Sydney Harbour on NYE, including the flying performance and another plane up high writing words.

So I want to ask how do ATC control these movements? Do they need to close the airspace to allow those?

Thanks.