hangfat

officially, yes you need a hk passport with a 回鄉證 if you go to china directly from canada., not just a 回鄉證 as it's not a international travel document.
but i know people go with just the 回鄉證 with no problem.
as far as i can remember, some people were denied boarding air canada some years ago, was on A1 page news in local chinese newspaper, as the agents (canadian) didn't know what a 回鄉證 was.
i called china eastern last year to confirm whether i needed a visa if i had a 回鄉證, stopping in shanghai , they said no. of course when you land in china , you don't show the immigration  officer both the 回鄉證 and the canada passport !!
by the way , hk passport can now go to many countries without a visa, may be more than a canadian passport, (russia , brazil and agentina ) to name just a few.
i guess more countries are FRIENDS to china nowadays!!
remember a canadian complained he didn't get any help from the govt in japan during last year's earthquate ? the chinese embassy there sent buses to evacuate the chinese including hk people in the affected area ?
so if you have hk id it's worth getting a hk  passport, and it's 10 years