Votes cast outside the electorate one is registered in -- from overseas, for example -- are transmitted to the appropriate electorate, tallied, and announced when the process is finished.

This may well tip the balance in a couple of electorates -- notably in Christchurch Central, which is a dead heat on election night, and is generally tipped to stay Labour once the votes of those displaced by the earthquake are tallied.  But this will not change the overall tally, as any electorate gained or lost will be compensated by the party's list seats.

BUT... traditionally the Greens do very well on special votes (such as mine). I haven't crunched the numbers myself, but here's a well-regarded blogger who has :

Election '11: the special votes * Legal Beagle * Public Address

Preliminary		Estimated
National	47.99%	60	47.46%	59
Labour	27.13%	34	27.29%	34
Green	10.62%	13	11.06%	14
New Zealand First	6.81%	8	6.59%	8
Māori Party	1.35%	3	1.43%	3
Mana	1.00%	1	1.06%	1
ACT	1.07%	1	1.05%	1
United Future	0.61%	1	0.60%	1
Conservative	2.76%	0	2.70%	0
		121		121

So as things stand, we are expected to pick up a 14th seat, at the expense of National.

This does not change the confidence and supply equation, as this has already been stitched up, as described above by Bruce. However, the government's ability to pass legislation is impaired. In the previous parliament, they had a stable, if thin, majority with National and ACT alone. In the new parliament, although National has gained, ACT was almost wiped out, and between them (if the Greens steal another seat), they no longer have a majority.

National's major campaign issue was privatization of state assets. It's possible that the sole "United Future" MP will sign up for this-- he's always been for hire in the past-- but he hasn't yet committed.

I would not have expected the Maori Party, who have been punished by their electorate for their support for National, to support the alienation of infrastructure, but...

Turia: Iwi want to be 'major players' in asset sales - National - NZ Herald News

Iwi want to be "major players" if the new National Government goes through with its planned state asset sales, Maori Party leader Tariana Turia says.

So according to her, their votes are for hire, as long as Maori tribes are allowed to be major shareholders. Sounds promising.

_{It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II}