Pursuant to section 52(3) of the Road Traffic Ordinance (Cap. 374) ("the Ordinance"), no person shall drive or use a motor vehicle; or suffer or permit a motor vehicle to be driven or used, for the carriage of passengers for hire or reward unless the vehicle complies with certain conditions stipulated in the Ordinance (including that a hire car permit is in force for the vehicle). Otherwise, it is an offence.

Therefore, if a cross-boundary private car does not have a valid hire car permit, it cannot be driven or used for carriage of passengers for hire or reward. Otherwise, it is an offence.

Any person who contravenes section 52(3) of the Ordinance commits an offence and is liable on a first conviction to a maximum fine of HK$10,000 and imprisonment for 6 months; and on a subsequent conviction to a maximum fine of HK$25,000 and imprisonment for 12 months.

Moreover, in accordance with sections 90 to 93 of the Ordinance, if a person is convicted under section 52(3), the licence of his/her vehicle may be suspended for a period of 6 months on first offence; and a period of 12 months on subsequent offence in respect of the same vehicle. The vehicle concerned shall be delivered into the custody of Transport Department during the vehicle licence suspension period.