There isn't any wiring as such, unless you mean to the pump? the pop-up spray jets are powered by water pressure.
Real oem shows the system http://www.realoem.com/bmw/enUS/showparts?id=BT52-EUR-06-2004-E85-BMW-Z4_30i&diagId=61_1604
When I needed those parts it was cheaper to buy a complete used bumper with the jets and covers (and fogs as it happened) for about £100, strip what I needed and sold on the grills, fogs and bumper for what I paid.
