Hi Josh,
The quality of the images through the API is determined by a couple of things, the quality of the cameras being used on the network in those locations as well as the image sizing we use for still images (to keep file sizes down). As we renew cameras on the network they will be replaced with higher quality ones - which means you should see the quality improve through the API. (Rushgreen camera is one of the newer ones -
http://nzta.govt.nz/traffic-and-travel-information/traffic-cameras/auckland/124)
The cameras that are used on NZTA social media are different cameras all together (while some are in the same locations as the fixed cameras that provide the still images for the API, they are actually different cameras), because these cameras are used for multiple purposes in operating the transport network it is not feasible for us to use these for the API.
Thanks for the question, and apologies for the delay in responding.
The InfoConnect Team.