On Telecom you don't have the "hand down" because Telecom's network is almost 100% 850MHz 3G. 2100 MHz 3G on Telecom is used for infill/capacity only and should not be considered as the main access to the network.
This is very different from Vodafone which in main centres (up until now) had 2100 MHz 3G only and 900 MHz 3G in other areas. Where 2100 MHz isn't available the handset will then step down to 2G since it doesn't support 900 MHz.
Very different cases. Vodafone coverage is a mix of 2G and 3G (in two main bands), while Telecom coverage is 3G only mainly in 850 MHz.
Don't be fooled though. Telecom 3G coverage is equivalent to Vodafone's 2G + 3G.
Great point. Plus, with data rates being what they are the only thing I ever do when not on wireless is maps, email and whatsapp. All of those things work fine on either 2G or 3G so frankly I'm not even aware when I'm connected to one or the other. Right now (at home in Te Atatu Peninsula, Auckland) I get a 3G or H connection. Usually 3G.
I'm on Vodafone.