Do you and the neighbours own these flats, or are you renting? If the latter, then the electrical installation, particularly (but not exclusively) those 'communal' bits' would be the landlord's responsibility. If it is rented, then I would have thought that the landlord would probably be on the wrong side of some regulations/laws by permitting that electrical installation to persist as it is.the neighbors wont be to happy with me costing them money to get it fixed if its working, although it is unsafe they will see it as working and the insurance will pay if it go's up in flames, on the other hand if its free there wont be a problem. how do you find out who owns it ?
...and don't take it for granted that, in the presence of an unsafe electrical installation, an insurance company would necessarily cough up if the place went up in flames.
Kind Regards, John