Well if you're notified for coming first in a subject, you'll most likely be scoring a Band 6 (on the honour roll). If you've come first for quite a few subjects, you'll be receiving a Premier's Award (the 'ceremony').
I should think that Premier's Award recipients are notified, before the release of HSC Marks, seeing as though some of them will 'double up' on receiving first place in a course. If you're first in a course, you'll be notified - if you're receiving a Premier's Award, I think that you'd also be told, in the one phonecall. I don't see why they should notify everybody on two separate occasions.
"You're on the honour roll! Congratulations!" (Band 6)
(tens minutes later)
"By the way, you're also first in the state! Congratulations"
(twenty minutes later)
"We forgot to tell you, you're getting a Premier's Award! Congratulations" (Band 6 in ten units or more).
I don't know how it works, but I'm sure someone'll post on BOS, expressing their delight.