I got to know of the email address virtual.ceremony.nsw@homeaffairs.gov.au from forums including this one, and not from the case officer.
During my interview, I asked the case officer if there is a way I can attend the next available ceremony, reason being is I am applying for a government job requiring a baseline security clearance which only Australian citizens can apply for. The case officer mentioned that I would have to wait for the invite coming from my local council. She (case officer) kindly checked how many are in queue in my council, and said there's 'quite a large queue' without specifying the numbers (I didn't ask either how many to be exact). Got home and I saw from the forums that I can request a virtual ceremony so I thought to give it a shot.