JQ is 100% owned by QF. Having the QF codeshares on some -- but not all -- JQ flights is part of the pretense that JQ is a separate airline and not operated as part of QF. This pretense is vital to the JQ labour model (otherwise the workers can claim that they are employed by QF and should get the same working conditions as other QF employees). There is no other reason, the whole JQ/QF structure is for the convenience of management and the (in)convenience of pax. Some of the QF flight services are mandated by law -- i.e. QF got past subsidies (some going back to when it was state owned) based upon providing service on certain routes; and those commitments are still in force. So QF must fly certain routes; but has discovered the codeshare loophole, letting it fly a virtual plane (with virtual service). Overall the discrepancy of QF on JQ vs. QF is simply too great, and I am surprised that it is allowed to go on. But that is politics in action.