We've not been here and available railfan info is scant. From the map the track laid in this garden doesn't look long, maybe a quarter mile (400 metres) and it's not clear if there are operating trains. Being built during Japanese occupation it's likely the locos were Japanese and cape gauge was used.
From the official website:
"Taipingshan’s forestry industry began in 1905, with the Forestry Agency of Japan drawing plans to harvest the area’s native cypress forests. A dragging track was built by laborers to pull logs up to a timber processing ground by the Duowang River. The log would then be transported out of town through the Langyan River. In 1921, the agency purchased a railway from the Taiwan Sugar Factory and adapted it for transporting timber. The railway was 36.95 km long, stretching from the timber processing ground to Tiansongpi, Waiziwai, and Zhulin Station. From then on, felling of trees was carried out on an immense scale and such continued for 68 years. Taipingshan stood alongside Alishan and Bahsienshan as the three largest forest areas during the Japanese Occupation, and its scale of felling was the greatest of all."