The financial arrangement is that BA would get a cut of the money that CX gets for flying the HKG -AKL leg.
Not that way around. A passenger booking this service will be travelling on a BA ticket - and will have paid BA for it, so BA will have all the money. For the CX operated sector, at some point CX will bill BA the agreed fare for HKG-AKL, which in practice will be offset by bills for CX ticketed passengers who have done, for example, HKG-EDI with CX/BA.
CX's flight HKG-AKL will operate as a pure CX service in terms of all airport/airway billing, callsigns, etc etc. The fact that BA have put passengers on board it matters not a jot - it is still a CX service. The codeshare thing is purely a marketing arrangement rather than an operational one.
Hope this helps
TA
