Can landlord cut the supply???

NO! Landlord can not cut off the utility supply to the rent out unit even the lease is expired.

According to the Laws of Hpng Kong, Landlord and Tenant (Consoildation) Ordinance Cap.7, if the landlord cut off the utility supply of the rent out unit, even the lease is expired, then the landlord is committed an offence. It is criminal offence. The right procdures should apply re-entry through court order from Lands Tribunal. You may also apply the recover of the legal costs and the current market rent for the period from the date of pervious lease expiry date to the actual date of re-entry.

In a first principle, yes. As the terms of the tenancy has expired, the landlord has no obligation to keep the premise in a lettable or usable condition as stated in the tenancy agreement. He could simply ask the water authority and electricity company simply stating that to terminate the contractual obligation for the supply of such utilities as the accounts are in his own name. He has an absolute right to do so. Of course, it is better to consult a lawyer's view before doing it as different scenarios will give different implications to legal consequences.