We landed at Magenta from Isle of Pines on a Friday night (~7pm) without having organised a transfer to our hotel and the airport was virtually closed i.e. no tourist information, bus shuttle counters etc.
We found out that cabs need to be prebooked in Noumea and that 'flagging down' a cab is not the custom. Luckily a cab driver called for extra cabs and we ended up taking a cab from Magenta to Anse Vata which costs ~$20 AUD. Still cheaper than the Arc En Ciel shuttle for 3,000 CFP per person.