The Taffmeister speaketh the truth! Check out the 'official position' on overseas telephones and modems here...
About Telepermit
This is what they say......
Q.1 "I'm coming from overseas and want to bring a "xx" with me" - are there any rules?;
Answer: Yes. Products sold on overseas markets do NOT have Telepermits and may not suit either the Telecom network or New Zealand regulations. At least some problems are likely, but local suppliers probably don't have the necessary spare parts or product information to service or modify the product. We recommend you sell the item in its home country, where it has some commercial value.
Q.2 "I've arrived from overseas and have a "xx" with me - what do I have to do to connect it".
Answer: Overseas products should NOT be connect to our lines. To do so is in breach of your contract with us. If you do decide to connect overseas products and trouble results, not only will we be unable to repair them, but we will charge you a service fee to cover any work we do in finding that your non-Telepermitted equipment caused the fault. If harm to our network or services is caused by your equipment, we have the right to charge you for any remedial action we take. Overseas standards and products may differ from our own in many respects. Testing and modification costs far outweigh the local costs of replacing the item with a local equivalent.
Of course, if your overseas equipment has been working without any problems in NZ for over 12 months, you might be forgiven for thinking that this is a shameless ploy to get you to spend your dwindling pile of disposable income on Telecom-approved equipment.....
(Blimey, that was almost a rant!)