Credit is assessed when you put in the course application. You'll get credit for a subject that is deemed to be an "equivalent" (e.g. extremely similar content taught). If you haven't done any "allied health" related units during your bachelor of science, there's a chance you won't get any credit at all and will have to start from scratch (unless there's electives/free units, and then you'll be able to fill them up with credit from your science degree).
It is a confusing process, I agree. I also agree with Euler that each area/department/faculty has different rules for entry. Transfers to another uni take into account the current course enrolment, your past academic history, prerequisites met for the new course etc. etc. etc.
Unis are very 'hush hush' in regards to advanced standing - and won't give you a definitive answer. I've tried to get answers before too (since I've considered transferring before both internally and externally).
If this isn't too personal - you stated that you're in your final year... why are you wanting to transfer out now? Would it be better to finish it off (since i'm assuming you only have less than a year remaining?).. You've come this far!