Actually the QF beard rule was challenged after the merger with TN.
TAA/Australian did allow beards and at least one particular F/A who had a beard, took the case to the AIRC with the help of the FAAA.
The beards lost unfortunately, and the oxygen mask and PBE seal was to blame.
Here's a link to the case:
http://www.airc.gov.au
080/isysquery/irl6e3/1/doc