The OW Lounge Access Policy clearly state first and business class passengers are entitled access to a lounge equivalent to the class of travel regardless of status, with some exceptions i.e Qatar and Finnair business light fares do not include lounge access and some Qatar and British Airways lounges are excluded:
OW Lounge Access Policy
QF, with its home port being Sydney, naturally operate more lounges and presumably normally accommodate more OW passengers in their lounges than any of the other OW airlines who have lounges in Sydney. If QF normally provides a business lounge at its home port but have substituted this for a first lounge (presumably because traffic is not high enough to warrant having a business and first lounge open) and is directing its own customers to use the substituted lounge, why not extend this to OW customers also?
QF would be aware foreign airlines would not have the same number of flights operating out of Sydney to justify opening their own business lounges at this time and, regardless of who pays, do not believe QFs behavior is in the spirit of being part of an alliance.