I believe that the National party in NZ believe that by implementing ACTA (that's essentially what this is) that they will curry favor in terms of a potential US free trade agreement. It's basically the US dictating intellectual property law to the world.

The reason to do it under urgency is that it's so incredibly flawed and unpopular, it probably wouldn't stand up to a normal democratic process. So by sidestepping the democratic process, it makes it much easier to get things done.