Your marks go through a 2 step process, although I wouldn't really call it 'scaling':
1st the department your subject is related to reviews the marks (E.g. depatment of pharmacology). This is more just to confirm that whoever marked the papers did so fairly and was not super mean or super nice in their marking scheme.
2nd the marks go to the examinors committee, they may make some 'slight' adjustments to marks if the distribution is way off the goal of a bell curve distribution of HDs, Ds, Cs and Ps, but largely they just collate and database all the marks.
As mentioned above you may get a slightly scaled mark for doing the advanced or higher version of a subject compared to the fundamental version. However it's not like HSC english, where only like 5 people in the state each year get a band 6 in standard english, in for example fundamentals of chemistry it is still fairly easy to get a HD.