A screenshot from a 1952 map at http://www.hkmaps.hk/mapviewer.html . Shows WWII shoreline pillboxes at the eastern (RAF) and western (civilian) ends of the old Kai Tak Aerodrome. I knew there were inland pillboxes on Kwun Tong Road near the entrance to RAF Kai Tak but this is the first time I have seen the location of the two shoreline pillboxes. The pillboxes may not have survived the war.
Date picture taken
1930s / 1952 ?
The shape of the nullah on the map at the bottom-left corner of the airfield looks very similar to the nullah in this 1944 aerial shot, which shows the airfield after the Japanese expansion:
So I think the map shows the post-WW2 shoreline in 1952. (These nautical charts are odd to look at. The sailors are interested in making sure they don't hit the shore, so they make sure the shoreline is right up to date. But they don't care what happens inland so areas of the chart away from the sea can be way out of date.)
Amended to 1952
Given the expanded airfield shown in the aerial photo that matches the map, the pillboxes on the shoreline may have been of Japanese design, similar to the one found at Tai Hom, Diamond Hill.