You will find several different countries of registration for aircraft based in HKG.
Privately owned/operated are usually N, VP or M registration. Licensing is through validation of a foreign license for VP and M, a simple process.
B (HKG) registration is limited to aircraft operated by companies with a HKG AOC, and you can expect that some of these frames are used for charter. There are no validations when operating B (HKG): you must go through a full validation, conversion and flight check process. The flight checks required are in a sim and in the actual aircraft, with a HKCAD approved checker. Your licence conversion must be sponsored by a HKG operator, so there is no point trying to get a HKG licence on your own initiative. HKCAD is a very conservative organisation, and there are no shortcuts!
B (China) registration is, as far as I know, not available to HKG based aircraft. If you are Hong Kong based, you shouldn't ever have to go through the CAAC licensing process. There are other threads that refer to this process...
Trivia time: how to tell the difference between the B reg jets in this neck of the woods:
Hong Kong reg aircraft have 3 letters after the B: either B-H##, B-K## or B-L##
Macau reg aircraft have 3 letters after the B: B-M##
Taiwan reg aircraft have 5 digits after the B (eg. B-12345)
China reg aircraft have 4 digits after the B (eg. B-1234)
Safe flying