It was explained at the ATCO Regulation Workshop in March 2015 that in the event of surveillance failure which results in having to switch to a procedural environment, once the failure is contained and the environment made safe, the provision of any further service would require an Approach Control Procedural (APP) or an Area Control Procedural (ACP) rating. What about if the unit or sector, operated in a rigid environment of 1 departure every 10 minutes, is to be handed over to a surveillance unit/sector and with no other traffic involved, would this be considered a requirement for the procedural rating?
As a rule of thumb, the provision of procedural ATC requires a procedural rating. It should be evaluated on a case-by-case basis, e.g. whether procedural separation/clearances/procedures would be used.