I’ve been searching for ways to get there but I can’t find much. Everything basically says that regular visitors aren’t allowed. I wonder if the OP’s wife has some connections?
I did find this website that offers tours, if they get enough people, but I have no idea if the information is still current: 好野旅遊 | 戶外活動最佳夥伴
They were nice enough to engrave this plaque in Chinese and English, meaning that foreigners are expected to visit! /sarcasm
