When there was a FSU, the FIR boundary I recall was in the vicinity of the island. I believe the FIR boundary was moved west to where it is now quite some years ago.
For at least the last 30 years the boundary between Australia and New Zealand (and for that matter Nandi) was 163deg East where as Norfolk Island is nearly 168deg East.
I can't remember whether Sydney Ops (old B60 at KSA) exercised operational control over Norfolk? Anyone?