http://www.scmp.com/news/hong-kong/e...le-it-yourself

"There have been cases where compensation offered to passengers in Hong Kong was actually less than the stipulated amount under the jurisdiction of the destination, but customers still accepted,” Wong said. However, according to her, upon finding out later that they were entitled to more, some passengers have complained to the council, and follow-up actions led to the airlines eventually paying the balance."

No airline was specifically involved but Consumer Council HK's ambit includes HK-domiciled airlines and foreign airlines operating out of HK, so to me this suggests HK Consumer Council will assist ex-HKG passengers:

1. Travelling on EU carriers to recover their EC261 compensation; and

2. Travelling on US or HK carriers to recover any US DOT compensation such as 14 CFR Part 250 IDB claims.