It varies for each university, and not all require UMAT for entry.
Griffith for example doesn't ask for UMAT, but its cutoff last year was 99.90 according to UAC.
Adelaide does require both UMAT and ATAR, at around 90th percentile and up and an ATAR greater than 97 I estimate.
The unis that do ask for a UMAT score have a lower ATAR cutoff, that is for sure.