This article on ABC news confirms that he was a DFAT contractor,
Queensland Premier asks police to investigate how '''security contractor''' was granted coronavirus quarantine exemption, three others charged - ABC News he had DFAT paperwork confirming his employment and had a diplomatic passport which would not be unusual. He does not however have any sort of diplomatic immunity because he isnt a member of diplomatic staff (not that this is relevant). Diplomatic passports are sometimes issued instead of Official ones depending on the vagaries of the host country.
The question of whether he should have gone into quarantine in Sydney raises the question of whether Danni Minogue should have been quarantining at her residence, similarly the Prime Minister, Marise Payne etc who also do not have to go into government quarantine but are required to self isolate at home.
Regards,
Tote