So what IP rating is expected / specified? - No IP rating is specified by the design.
So the client has purchased IP rated cabinets with what IP rating? - The client purchased cabinets that are not IP rated which is why the issue was raised.
Apart from the hole cored through the platform what other part of the base is open - There is a hole in the side towards the top, that a bolt enters through. Water ingress unlikely, but theoretically possible.
It is very easy to guess and assume possible outcomes, I can never recall condensation being a problem in an outdoor enclosure containing equipment that produces a lot of heat, you are more likely to have problems of kit overheating from a lack of ventilation - overheating also possible, primary concern is cold air touching a warm surface and dew forming. People get it in their houses where the wall is cold and the room is warm, black mould can form in poorly ventilated corners, it does happen.
Every enclosure has an IP rating even a consumer unit has one, without knowing what IP rating the job spec calls for it is difficult to comment. The job does not call for an IP rating. The client has decided the enclosure, although not IP rated, is fit for purpose. It has a good door seal and they've installed similar elsewhere 'with no problems' i'm told.
So one minute you are telling us that the client procured IP rated cabinets and now you are telling us he has used "similar" non IP rated cabinets on other jobs. Have all these jobs been for the same customer as I can see an even bigger argument brewing if cheaper cabinets of a lesser IP than specced have been used on these jobs - No this is a miscommunication / misunderstanding, the cabinets do not ship as IP rated but do seem quite rainproof.
It must have some IP rating even IPXX - You would think, but i contacted the manufacturer and they confirmed they are not IP rated due to the open base.
So the cabinet has a minimum IP rating what is the minimum IP rating required by the engineer - zero IP rating on the cabinet, any kind of IP rating recommended by the engineer.
So whose design / installation method is this - the client insisted the design house specify this particular cabinet, don't really want to give names.
Does this cabinet not have a plinth to raise it off the ground - no, straight onto smooth concrete
So a Roxtec or similar cable transit will close the hole and also seal the cables using the appropriate cable blocks - I was advised today that they are going to seal the core hole, which will help a lot and give it some kind of functional equivalent of an IP rating, but it will still not be an officially IP rated enclosure.
There are regs regarding IP ratings but you have not indicated what the expected or specified IP rating is in the job spec - minimum IP rating will suffice.
Not sure how to carve up the coloured sections but have added my responses above, thanks for your input