According to Section 5 of VTAC's
Privacy Policy:
Your information may also be shared with any organisations with which we are required by law to share the information.
As for mandatory reporting, according to
the AIFS website:
Legislation in all jurisdictions except New South Wales requires mandatory reporting in relation to all young people up to the age of 18 years (whether they use the terms "children" or "children and young people").
And is required in Victoria if:
Child has suffered, or is likely to suffer, significant harm as a result of physical injury or sexual abuse, and the child's parents have not protected, or are unlikely to protect, the child from harm of that type
So I do believe if the experiences that you described are ongoing today, VTAC is likely to be bound legally to report such information to public services. If they are in the past, however, and you are no longer in immediate danger (as defined in the quote above), it may not be reported.
It might be beneficial to you to write anonymously to a legal assistance service in Australia to clarify your rights to privacy in this situation.
Good luck