Well, in Australia they won't allow you to transfer a HKG driving licence on its own. you need that certificate, faxed to your transport depot, upon receiving it, only then, will they transfer to a local driver's licence.
Took a bit of mucking around, but as I have family in HK, so wasn't too bad. Took about 10 days for the HKTD, to send the Fax to our local Qld TD branch office.
Not sure what you can do about this if you're not in HK and don't have someone authorised to pay the fee, submit the application and collect it.
The certificate must be faxed by the HKTD to the fax number you are given when you apply for transfer. Apparently the HK licence has been counterfeited quite a bit, so they want proof now.