My question is irrelevant anyway as the airport website shows Air France and City Jet are moving to Terminal 3.
However I would still suggest for example is you have a Qantas flight number on a BA flight from say London to Hong Kong you will fly from T5 and not T3 as with a normal Qantas flgiht (forgive me if I have the wrong terminal at Heathrow) merely an example of my point.