Found a council hazard report. Also says power comes from Maraetai. No mention of where the telephone cables are but I found this:
nfrastructureThe island has less infrastructure than mainland Auckland. The roads are mainly narrow and in many places unsealed and unlit, especially on the eastern half of the island. The Waiheke Bus Company (owned by Fullers) services most inhabited parts of the island, linking to the ferry sailings from Matiatia.
Waiheke is connected to the North Island’s electricity network via twin 33 kV undersea cables from Maraetai on the mainland, terminating on the