As far as I am aware, the University of Cambridge does not consider the UCAT for admission to its School of Clinical Medicine. Instead, all Standard Course applicants are required to sit the Biomedical Admission Test (BMAT). In terms of academic requirements at year 12 level, typical offers for applicants whose ATAR is considered would be based on a rank of 98.5 - 99.5, alongside documentation of similar performance (in the case of NSW, favourable HSC marks, most likely within the band 6/E4 range) in relevant subjects (in the case of medicine, these can include Biology and Chemistry). Here, one can notice a few differences with NSW universities such as UNSW and USyd. For example, UoC does not only seek a favourable final result (such as a high ATAR). It also requires evidence of favourable performance in individual subjects relevant to the degree, as opposed to UNSW, which emphasises assumed knowledge. While USyd does have prerequisites, those only apply to mathematics subjects, being a band 4 in Mathematics Advanced, band E3 in Mathematics Extension 1 or band E3 in Mathematics Extension 2. UoC's individual subject requirements extend to all relevant subjects in addition to mathematics while imposing a higher standard compared to that of USyd.
Additionally, while UoC does not require applicants to undertake relevant work experience, the university strongly advises applicants to undertake relevant work experience (either paid or unpaid/voluntary) in a health or social care organisation in order for applicants to gain an understanding of what a career in medicine entails. This is not something that is emphasised by NSW universities that offer a Doctor of Medicine program.
Lastly, a similarity between the aforementioned universities in terms of their respective medicine programs is the need to attend an interview. Overall, given all of this information, it seems that entry to UoC's Standard Course is more difficult/demanding than USyd and UNSW's Doctor of Medicine programs. The following links also provide some useful information for you to have a look at if you wish:
Take your first step to a career in medicine. Gain scientific knowledge and skills, then apply them on clinical placements in hospitals and GP practices.
www.undergraduate.study.cam.ac.uk
Before applying, you need to check that you have, or are likely to achieve, the right grades at the right level and in the appropriate subjects for the course you have chosen. Check the requirements of your course for details. You should also check whether you need to take an admissions assessment.
www.undergraduate.study.cam.ac.uk
This article goes through everything you need to know about Cambridge's academic and non-academic requirements to study Medicine at their school.
www.ucatmasterclass.com
I hope this helps!