All North American BMW E39s 5 series ARE prewired for telephone, while some Euro or Rest of World BMWs may not be prewired for telephone.

If your E39 is not prewired for telephone, the E39 wil simply need a special wiring cable harness that connects to the telephone power connector in the back of the car.

These custom wiring cable harnesses can be found from online retailers. A web search for "bmw e39 bmw bluetooth custom made" for options on obtaining the proper wiring harness for your car