...

I think it's a little difficult to be entirely sure about this without more information about the particular building.

Certainly, the term 'demi-étage' is very often used to refer to a sort of intermediate 'mezzanine' floor (cf. half-landing) — which would be consistent with the kind of high-ceilinged premises commonly found in warehouses etc.

However, organizing it 'par plateau' sounds odd; one would usually expect 'plateau' to be a floor, but surely the type of building I'm thinking of doesn't usually have high-ceilinged floors other than at ground level. I'm wondering if 'plateau' is perhaps being used in a different sense here, as this is in connection with logistics? Perhaps each division of the warehouse has its own office space up on a mezzanine level.

Also, why would putting the offices up on a mezzanine floor (a very common practice, of course) actually help communications? one might have thought it would do the opposite...

I think there could be more to this than meets the eye, and suggest that Asker should perhaps try and get a picture or plans of these premises, or maybe see if there are any other clues elsewhere in the document.

This is how I understand it. 'Organisé' = structured or, other words-built/constructed. 'en-demi étage'= semi -floor, half a floor if you prefer. I hope is what you are looking for.