here you can find an overview for all the different countries Belgium has an agreement with (including the HK documents).
http://www.fisconet.fgov.be/nl/?fram...type=verdr!INH&
You can see there is a more up-to-date circular for HK which basically tells the same :
Income, not being dividends, interest or royalties, which is taxed in Hong Kong in accordance with the provisions of the Agreement, shall be exempted from tax in Belgium