@QF94: "QANTAS competes with airlines that fly to Europe from SIN, HKG and BKK. Does QANTAS compete with South African to Johannesburg? NO. They code share out of Sydney on a QANTAS plane, and codeshare out of Perth on a SAA plane."
Qantas competes with the following when passengers fly Aussie to Johannesburg/South Africa: Singapore; Malaysian; Emirates; Cathay & maybe others too. How do I know - I have friends and family who have all used these airlines on the route in the last year. Sure, some flights take 12 to 18 hours longer, but many people treat a stopover in a never-before seen city as an adventure.