However, according to Mike Williams, an oceanographer of National Institute of Water and Atmospheric Research [wiki], the chance of those icebergs to hit the country is very low:
"It's a natural but a rare phenomenon. It requires a lot of rare occurrences to happen simultaneously. This iceberg has to have managed to make it to the right place in the main currents in the Southern Ocean to have gotten all the way around to New Zealand without melting."
"Then, it has to have moved far enough north to have got pushed up towards New Zealand rather than pushed further south which is what happens to most icebergs."
Link (picture source: China daily)