NZ can also trade its geographic location to the US and UK to offer them full civil, naval and military satellite intercepts in the region.
For that NZ gets huge hardware and software upgrades it could never afford and gets to share in the raw material of interest to NZ.
US and UK staff also get to be "attached" to the NZ effort and can see the world and help with collection around the world. Generations of staff get an understanding of regional telco systems and bulk US/UK collection globally. NZ faced new cypher machines in Japan and had to work hard with the US and UK to get back in the 1980's.
NZ is looking for everything in real time just like the US and UK. Different diplomatic cables might be of more interest but NZ is getting everything in the region and beyond. The prestige of raw traffic.