Can't speak for anyone else but we did a fair bit of work including a PIA before we allowed the use of bodyworn cameras. the PIA was refreshed recently with a change in technology and we insisted on changes to the proposed method of working. i.e. We've forced the cameras to be used in such a manner that no data is retained unless the operator hits a button. A bit like dashcams in cars these cameras so record in a loop continuously but when something kicks off the operator can hit a button and the previous minute is retained then until the incident finishes.
What I would suspect happened in many places is what happened here, that is, the services that want cameras go out an buy them without asking anyone or telling anyone then get caught red handed trying to get them installed reported to the DPO who then has to spend months sorting out the legalities all whilst the service that was wrong in the first place drags it's heels kicking and screaming because they've been shown up and can't use their new toys exactly how they want to.
So those that have them in without policies or PIA managed to sneak them in without telling anyone and have now been caught via FOI. Expect a massive scrabbling for retrospective PIAs