My first thought was...
I could imagine this being an intermittent sentry point between the Batteries of the Peak and Pok Fu Lam Reservoir encampments (primarily the Forward Dressing Station noted by Dr Solomon Bard) I thought about A. H. Pott's wartime diary.
Location of marker is approximate. This building is clearly marked in the GeoInfo Map. Most likely in current 1:10000 & 1:5000 maps too.
Walked by this Forward Dressing Station on 12th February. It would seem it might have been used by squatters after the war. At that time and before the housing developments, the slopes are full of huts and terraces. The terraces are much over grown but still visible if you know where to look.
