Hello
I'm a student ambassador for the University of Sydney, and I have quite a bit of experience working with alternate pathways.
There's no certain ATAR concession for any particular degree available for these entry schemes-- but rather the University just fills-in the set amount of places for each degree for each scheme. With law specifically, I believe that an ATAR in the high 98s to low 99s makes you competitive for the degree. However, ATAR-cut offs are decided by demand so nothing is set in stone
The scheme works well if you have a higher ATAR, because that means that there is a higher range of choices.
Hope this helps.