Firstly, I wasn't specifically referring to immigration, rather the general lack of recognition in HK for common-law relationships. Since HK prides itself so much on following western developed economy standards, it seems quite retrograde for it not to recognize this one - particularly since it is a fact of life for many of its residents, whether or not the government likes it.
So KnowItAll, not to appear ungrateful of your information, but why such a dismissive hostility to the idea? You may "see no reason for HK to follow", but the thousands of people living in such relationships in HK today (whether you like it or not), would undoubtedly disagree. It's always easy for people to be dismissive when its someone else's rights that are not being respected.
As for me, the first step is getting information, which is what I'm doing here. I will take it up with the government, I can be quite a persistent pest on such issues. No need to start a vigil. I'd be most surprised, however, if there isn't already a movement afoot that I can lend support to. Anyone know of any such groups interested in this issue?