For what it is worth, this number originally did not work when calling from Vonage lines. I asked Vonage about it and eventually they got it working correctly. It stopped working again recently, and when I e-mailed them they had it working again in about 2 hours. The 2nd level tech called and explained to me that Vonage now routes this call through their London switches - where it seems to work correctly for connecting to HK. Round-about for sure, but at least it works!

So the moral - if it doesn't work on your lines - try calling your carrier - they may be able to get it working for you as well.