Aside from the fact that this was not turbulence-related: my understanding is that other airlines in the area inform each other about turbulence they experience, as it cannot be detected reliably. A flight from Chile to New Zealand probably has very little air traffic to keep other pilots informed about the state of winds.
The incident happened while still on the Sydney to Auckland leg of the trip, which is not as lonely (but yeah, still not a whole lot of planes going each way).
