Thanks for your enquiries regarding DNR orders. I work with Felix at the Cancer Council and we were really sorry to hear about your father's experiences. We have received some advice from our legal advisers about this issue.
Basically, under the law, each person who is considered mentally capable of making a decision is entitled to make their own decision about whether they refuse or continue life-sustaining treatment. A person can also change their mind as long as they are still mentally capable of doing so, which means that even if you have previously signed a DNR order, you can later write a new directive that specifies that you do want to be resuscitated and receive life-sustaining treatment. If you don't write a new directive, though, any DNR order that you have previously signed will still be in effect.
NSW Health has issued guidelines for end-of-life care and decision-making which include the following as a guiding principle:
The right to know and to choose
All persons receiving healthcare have a right to be informed about their condition and their treatment options. They have a right to receive or refuse life-prolonging treatment. Caregivers have an ethical and legal obligation to acknowledge and honour these stated choices and preferences in accordance with these guidelines.
A link to these guidelines is here. Both public and private hospitals are expected to follow these guidelines, but they are not legally bound to do so. If you are asked to sign a DNR order, and you do not wish to do so, you should raise these guidelines with the relevant hospital.
However, when you are dealing with private facilities, they are of course not obliged to treat you and can impose conditions on the acceptance of patients (including that a DNR order be signed - although this would be quite unusual). It may be that the private facility in question raised the DNR issue because they were trying to explain that they do not have the appropriate resources to treat patients who need to be resuscitated, and that if this is the patient's wish, then they may not be the appropriate facility.
I hope this is helpful for you.