No JQ pilots will be flying the QF aircraft, but QF can put some of its people onto JQ aircraft (with their C&T pilots) for the very few flights that each person will need. It will literally be one or two sectors for many. When the A380 was introduced, a small group flew the Airbus test aircraft for 10 hours each...and it was a totally new type. Malaysian provided sectors for the A330, and we trained the initial BA 380 batch. Once the first couple of aircraft are in service, training will be non-stop on them for a while, but there's no need for it to be 'outside' at all.
Perth isn't really relevant to the initial introduction. The first route is Melbourne - LA, and 787s are very common at both ends. Whilst I'm sure there will be some odd flights, there's no need for many.