Hi Chee
I contacted PCCW before on this question and they said they can use the existing jacks in the flat from HGC. Beware that someone in RC has switched to PCCW and found out that you must use the Cat 5 wire that was provided from the RC management office or have PCCW rigged you another one as not all pins can be "connected" as it can conflict between the HGC broadband and the telephony service. Not sure if this holds true even for HGC telephony service though and I can run a test later on.
Despite the lousy HGC services I decided to switch from PCCW to HGC for my telephone/fax service in my RC flat to avoid future "conflicts"