I'm not quite certain I grasp the precise wiring configuration here.
Is there just some sort of balancing arrangement between the phases to derive a neutral, or is there a grounding conductor to the wye panel and then the neutral is "borrowed" from the panel frame/ground as C-H is suggesting?
The latter arrangement would certainly not be to "code" in the U.K. where neutrals and protective grounding conductors must be kept strictly separate beyond the service entrance. Italy? No idea......
