This is a Grade 2 historic building, which was built in 1906 and is still in use.
The Historic Building Appraisal states that it was "constructed for the accommodation of the managerial staff engaged on the construction of the Kowloon-Canton Railway. The house and the adjacent guest bungalow and servants' quarters sit in 6 acres of grounds close to the railway and some 167 steps lead up to the site from the old railway station of Tai Po Kau. After the completion of the Railway work, the house was no longer required for that original purpose and it was taken over by the Government to become quarters for civil servants. At first the house was named White Cottage. It was renamed as White House sometime around 1935."
Its various uses in the intervening years are described in the Appraisal. Since 1999, it has been used as a family retreat centre (managed by the Hong Kong Family Welfare Society) and called the 'Zonta White House'.
(the full Appraisal is here: http://www.aab.gov.hk/historicbuilding/en/N143_Appraisal_En.pdf)