Comment 43 for bug 1173571

Actually, so far this bug has resulted in the changes stated in comment #21, #24 and #26, so Droid Sans Fallback is indeed used in zh-hk already.

http://bazaar.launchpad.net/~ubuntu-branches/ubuntu/trusty/language-selector/trusty/view/head:/fontconfig/69-language-selector-zh-hk.conf

It's also installed by default for all users of the Ubuntu desktop. Hope you'll find that we are on the right track. ;-)