Hansen laid down the marker with a 58.7sec clear round with Cubit, second into the arena, shaving just 0.76s off the time.
No other combinations managed to go clear.
There was drama in the first round, with Tauranga's Samantha Morrison suffering a fall at the last jump.
Tauranga's Sally Steiner and husband Phillip, part of the team of event organisers, also rode in the Grand Prix. Sally said the whole four-day event was a great success.
"It's been exceptionally busy - they have been very long days, but there has been good competition on a good ground and all the competitors have been really happy."
"Our course designer, Australian John Vallance, who co-designed the course at the 2000 Sydney Olympic Games, has done an amazing job of creating a course that has encouraged good competition."
Many riders were using the event as part of their build-up to the Horse of the Year Show in Hastings from March 17-22.
Grand Prix result
1, Lisa Cubitt, Mon Deja Vue 57.94s; 2, Bridget Hansen, Shakespeare NZPH 58.7s; 3 Helen McNaught, Carnutelabryere 55.41 (4 penalties); 4 Bridget Hansen, Toulon NZPH 61.99 (4 faults), 5 Lisa Cubitt, Bates Amaretto MVNZ 62.93 (4 faults), 6, Olivia Robertson, Nahiwi Cisco - best rider from first round.