Wiring Diagrams at last!
Here are some sample wiring diagrams in PDF format.
As has already been said, the factory-fitted 6FL option uses both the TCU unit and the ULF-SBX-High unit in parallel. The latter box is only there to provide the 6FL capability (so presumably its other capabilities are ignored or are duplicated by the TCU).
I have included the standard (non-High) ULF-SBX diagram for completeness.
The power wiring schema is in separate diagrams which I can provide if anyone is interested.
It does seem that the European 6FL retrofit works in a different fashion to this.
For reference these diagrams are from 09/2007.