Just realised my last response may not have answered your question.
If your MOD quals are based upon the same range of competencies, and to the same depth as an Aus Aircraft Technician, then your quals will most probably equate to the Cert IV.
The competencies are available on-line under the following web-site:
www.ntis.gov.au
If you want to PM me, I will provide further guidance.
Spanner