Was looking the other day for a Spark tower I'd seen on the gis.geek map, but the tower itself doesn't seem to be where the map says it should be, and in fact I can't seem to see a Spark tower anywhere nearby, despite those frequencies being registered for a long time. Are those coordinates sometimes not on the money?

Looking at the spark coverage map, there does seem to be good signal around that area. 

https://gis.geek.nz/map/celltowers/location/zdwjxppw

https://www.topofthesouthmaps.co.nz/app/