Vodafone are the most global Telco Australia has, yet their global roaming rates have historically been obscenely high, just like their competitors. Today they've made a small dent to those charges by introducing standard local call charges for customers calling Australia from Singapore or New Zealand.
They've also adjusted data charges for New Zealand travellers, offering the "bargain" price of $2 per MB.
To get the discounted, you need to opt in to the Vodafone Traveller service before you hop on the plane. The local pricing are only available on postpaid outbound calls - you still get charged to receive calls as well. While it's still a far cry from being consumer friendly, at least Vodafone are cutting prices rather than raising them, I guess...