Hong Kong is using the GSM network. You can explore a wide range of packages offered by different service providers. When you sign a contract with a service provider, you are normally requested to show your Hong Kong Identity card, passport, proof of residential address in Hong Kong, etc. As an alternative, you can purchase a roaming pre-paid SIM card.
The following are some of the major mobile phone service providers in Hong Kong for reference only:
China Mobile Hong Kong Company Limited
CSL Mobile Limited
SmarTone Mobile Communications Limited
Three Hong Kong