I took my santa cruz superlight out in a planet x bike bag; complete with bivy bag, sleeping bag and clothes for a 16 day outback tour in South Australia. I phoned quantas and told them that i was doing a charity event and my bag weighed 32kg (and i weighed 10 stone) and the made sure that i wasn't charged excess baggage. the was in 2002.
MAKE SURE YOUR BIKE IS CLEANER THAN A SHOWROOM MODEL, otherwise customs will give you a lot of grief.