The current snap in adapter for the 3Gs is the 682. The 683 adapter is NLA. An interesting fact (generalized statement here) on this is that the iPhone adapters that ended in a 2 were for charge phone only and the adapters that ended in a 3 were for smart phone integration (6NL option usually). The 682 is the replacement for the 683. And when you open it up, the usual 3 wires that went from the PCB to the iPhone dock for charging have been replace with a ribbon cable that contains 15 'wires' coming back to the PCB that connects to the eject box. This would explain why the 682 now supports the smart phone intergration option on the newer models.
Of interest is that there is a smart phone retrofit kit (sorry part number on yellow sticky at work) which appears to replace the console eject box to allow the intergration to the iDrive/CCC/CDC. However BMW will not sell anymore to Canada due to customer dis-satisfaction. It would be interesting to get ahold of one of the kits to see what is contained and what signals are coming from the eject box.
I have not yet had time to trace out the ribbon cable on the 682 to see what pins on the iPhone dock it connects with and what contacts on the PCB/eject box conector it connects. This adapter opens up some interesting possibilities.

Apologise to X5 Meister for not responding to previous questions. Have sorted issues with not receiving alerts from Xoutpost.

Craig