That changed months ago. When the new smartgate exit machines were installed (the one step ones), premium immigration lane for other airlines was moved from the left hand side to the right and shared with NZ.

Unfortunately the new system isn't working properly. Last week there was only one officer on the shared premium immigration and she directed all non-NZ pax to join the regular immigration lane (non smartgate). Thus actually slower than just going directly to the regular lane or to using smartgate.