16Any requirement under section 4 of the [1973 c. 62.] Powers of Criminal Courts Act 1973 (attendance at day training centre) which is included in a probation order in force at the commencement of paragraph 1 of Schedule 11 to this Act shall thereafter have effect as if it were a requirement imposed under section 4B of that Act specifying as the day centre which the probationer is required to attend the day centre at the premises of the day training centre.