No - under the Rail and Other Guided Transport Systems (Safety) Regulations 2006 there is no concept of an external body inspecting or authorising modifications in this way. Provided that the (mark 1) coaching stock is covered by the relevant Regulation 4 exemption of the Railway Safety Regulations 1999 (which is crashworthiness related) and the operation, fitment and maintenance of such a system is suitably covered in the railway operator’s Safety Management System it can return to use if central door locking is fitted.
ORR approval is only required if another Regulation 5 exemption is to be issued, in which case as per other operators a time-bound, deliverable plan for fitment is essentially the only thing required to satisfy this.
ROGS essentially put the onus for certification and conformity on the operator, removing the previous practice of an HMRI inspector coming round and signing it off. The ORR could still carry out spot checks to see both paperwork and operation, but it isn’t a (legal) requirement to entry to service.
The ORR certainly didn’t give approval for last year’s hybrid operation of CDL mark 2 and non-CDL mark 1s.
All that said, if you’ve been in the spotlight of the regulator previously and had a very well publicised battle to avoid fitting CDL, it would probably be in your interest to invite the regulator round for a tea and a walk about…
It should be noted that with the exception of the North Yorkshire Moors Railway there are no longer any active Regulation 5 exemptions.