2006 C220 TDI Sport (in Germany)
When we purchased the car, one year old, we had the dealer install in the center console the cradle that fit my wife's old Nokia phone. Not a Bluetooth rig. My wife got two sim cards and just leaves the old phone in the car all the time. Works great, all the factory buttons work, etc. We negotiated this in the deal when we purchased the car (used), but were told it was maybe a 300 euro cost.
Based on the following, I believe the pre-wiring for the European models is different than the pre-wiring for the U.S. models. OR, the dealer from whom I am purchasing my 2007 C230 Sport is full of it. But I got the following story from the service department, not the salesman, so I put some stock in it.
I have purchased for my wife a 2007 C230 Sport, nearly the exact same car (OK, it's not a diesel) as we have in Germany - it is being delivered today. It has the 320 Entertainment package which includes the 387 Std. Cell Phone Pre-wiring. The Mercedes dealer, a five star dealer, tells me to install the cradle or the bluetooth option they must run a cable from the "pre-wired" connector under the dash to the trunk, install a "box", run the cable back to the console, and install a cradle (or bluetooth device). $1500 to $2000
A big difference in cost, which leads me to believe the European models have "more" in their pre-wiring package. Or my car here in Germany had the pre-wiring option plus some extra bits that were ordered from the factory when I bought it. All I know is when I purchased the car with 12,000 miles on it it was simple to add the cradle.
I think my wife is going to do without - BUT, the dealer also said there are some good aftermarket bluetooth products/devices available that will hook into the factory connector (I think) and allow use of the factory buttons. Maybe at a cost of $400 to $500.
I am going to try to find a trustworthy high-end car audio installer in my new town next week (as I move from Germany to America on Monday). See what he says. For $400 I make my wife happy. For $1500 she uses her bluetooth earpiece!
I'm trying to understand better your case, I believe the Euro car had the 386 option which in practise means everything except a phone specific cradle (or a BT adapter). A phone specific adapter was attached to the UHI connector in the car and a phone that fits to that connector. This car would equally accept a modern BT adapter.
But this feature is not standard in Europe. Actually at certain point US cars used to have the wiring placed in the car while the wiring too was an option for Euro cars. The wiring (antenna plus microphone etc.) allowed a relatively easy option to retrofit the phone kit. Basically only the control unit had to be installed an usually the UHI connector with relevant panelling at the centre console compartment (and version coding).
But the wiring seems to have been omitted from later US cars and the prewiring option (just the wiring harness plus microphone etc.) was dropped from the Euro options, the complete phone kit of course remaining.
The sticky thread from Skylaw (at Audio & Telematics) probably explains the US codes, I thought 387 in the US would be the same as 386 for Europe. But EPC tells 386 is "mobile pre.-installation (MTUS)" and 387 as "mobile pre.-installation (MTUS) USA/Canada" and 389 as "mobile pre.-installation (MTUS) USA/Canada Compl.", so is it actually 389 that is the complete kit equal to 386 in Europe.
If 389 is the whole kit, the 387 code should have the wiring that the dealer was talking about. The control unit and other parts would still be quite expensive but the installation task would not be that significant.
I'd suggest to wait for comments from US experts about this 387 code and the cost for an MB phone kit for this specific car (the sticky I was referring could already have the info).