Based on the published rules you may be able to swing it even though the lounge finder says no. The main issue is that there is no domestic business class in NZ so they may argue that it isn't a business class lounge. Worth a shot though.
Paid Lounge Membership Customers: Eligible Paid Lounge Membership Customers have access to any Star Alliance member carriers' owned Business Class lounges.
* Eligible Paid Lounge Membership Customers include United Airlines Red Carpet Club, US Airways Club, Air Canada Maple Leaf Club – Worldwide and Continental Airlines Presidents Club.
* Customer must present a valid eligible paid lounge membership card
* Customer must also present a boarding card for a same day Star Alliance flight departing from the local airport.
* Customer is entitled to one guest