Thanks Laurice! My pleasure that you find this story interesting :)

The data are exported from the "Build Your Own Table" web app in the census webpage (https://www.bycensus2016.gov.hk/en/bc-own_tbl.html).

The classification is a bit unintuitive in order to get the raw data of the OD matrix though - you need to search for the working population dataset, then classify the population by "District Council District" (Origin) and "Place of Work" (Destination).