Well here is my slant on all of this.(sorry, it's long !)
We used to undertake the CP and AP work (seperate people - 'cos it has to be)within the Med eng function at the Trust.
For various reasons (mainly available staff time and increasing medical equipment inventory)this has now been handed back to engineering colleagues in Estates, who maintain the distribution work as required under HTM 2022 (the standard was HTM 22 when we were involved).
Overall the permit to work system is in place to ensure the a formal system of work notification/ authorisation and documentation is in place to control piped medical gas systems work.
It involves an AP a CP and QC work, all of which are seperate duties and provide cross-checks on each of the work roles if carried out correctly.
Is it worth going there for and EBME function, - well that can depend on a few issues, such as :-

Staff training and competancy, tooling, permit system, management support, maybe a chartered engineer thrown in there somewhere (?).
Then it is worth considering who is going to look after the 'plant' equipment :- Air compressors, receivers and dryers, changeover manifolds, Vac pumps and receivers, VIE (bulk liquid Qxy)and so on.
There are quite a few aspects to manage, in all of this as you can see.
Best advice for me, is from places like Eastwood Park (use to call it Falfield when i went !) they run excellent course for all aspects of MPGV management and maintenance and I attended some of these in the dim and distant past.
In my humble opinion, If anyone wants to do PMGV , don't be worried about it , but just do it right, or don't bother at all !
(P.S. External contract costs can be quite large for this type of work, and there are benefits for organisations, in taking some/all of this work in-house, but again this is no place for 'half a job' with this work)
(P.P.S. we now only look after all of the stuff 'downstream' of the Terminal Unit outlets including Therapy regs/Flowmeters/injectors etc, which seems to be more of the norm these days, however we still have a set of 'metered leaks' - bet no one remembers them ???????)
Best wishes -
Steve.