There is a rather unusual legal position regarding Aus Post and new suburbs (even existing ones I suppose).

I had a problem with delivery to a location in NT where the item was RTS.

Turns out that AP need approval from the local council before delivery services can occur.

Perhaps under certain circumstances said permission can also be withdrawn?

But in short, yes, there can be problems delivering to new susburbs though it is fortunately a very rare occurrence.

Usually these arrangements (permissions) are sorted out before mail deliveries are required.

If you have a customer who is experiencing difficulty receiving mail they should contact Aus Post.