The Finance and Expenditure today released it’s report back to Parliament on this bill, including the FATCA enabling legislation. I have not had time to read it in full, but the short version is that all of the submissions opposing FATCA and the IGA were rejected.
The report states:
About half the submissions we received on the bill concerned these
FATCA-related provisions. Much concern was expressed that providing
such information would breach individuals’ privacy rights,
and constitute a form of discrimination contrary to the New Zealand
Bill of Rights Act 1990 and Human Rights Act 1993. It was argued
that the proposals would entail the release of data about spouses and
children who were not “US persons” in American tax law. More
broadly, the view was expressed that the US system of taxation
based on citizenship rather than residency is unjust, and that FATCA
and the inter-governmental agreement impinge on New Zealand’s
sovereignty and should not be accepted.
On the other hand, the financial services industry was generally supportive
of the proposals in the bill, expressing the view that failure
to comply with FATCA is not an option. Non-compliance would entail
significant penalties, effectively amounting to a 30 percent tax on
banks’ investment and funding income from the USA, which banks
rely on to provide mortgage finance and commercial loans in New
Zealand; it would therefore adversely affect New Zealand citizens
more broadly.
Assessment
We considered these issues carefully, seeking comment from the
Ministry of Foreign Affairs and Trade. While we sympathise
with the concerns, and initially shared a number of them, we have
reached the view that the proposed inter-governmental agreement,
and the amendments proposed in this bill to implement it, are in
New Zealand’s best interests. We therefore support the proposals in
the bill, recommending just two relatively minor amendments.
The full text can be found starting on page 12 here: http://www.parliament.nz/resource/0002241958
Perhaps of more interest is the IRD report on the submissions, which can be found here: http://taxpolicy.ird.govt.nz/sites/default/files/2014-or-arearm.pdf. The FATCA section starts on Page 109. Asking the IRD to review this was pointless in my opinion, it should have been done by an independent group. Some excerpts:
The proposals attracted more than 50 submissions, mostly from individuals (including some from overseas). Submissions from these individuals were unanimously opposed to FATCA and the IGA and, by extension, the proposed changes.

It seems obvious from submissions that many of the individuals concerned do not consider information-sharing in this case to be appropriate. However, government is in the position of having to make such judgements on a national, rather than individual, level. As set out in ―Entering into an IGA‖ section of this report, officials consider that a sound public policy argument exists in this case that justifies New Zealand entering into an IGA – a necessary part of such an action being that the information collection and transmission contemplated in the IGA will occur. The privacy of the individuals concerned was a factor that officials examined in reaching this view, but it was, on balance, deemed to be outweighed by other public-interest considerations.

The United States model of taxation is not new, so it appears reasonable to assume that citizens of the United States are aware both of their citizenship rights and obligations.

Recommendation
That the submissions be declined.
I would like to thank everyone here that made submissions to this bill (to no avail).