Can Bus Topology in the Vectra

I have found a very interesting document here: it is about the testing architecture developed at Opel for the Vectra. They call it Hardware-in-the-loop (HIL) simulation. Basically, due to the increasing number of ECU (Electronic Control Unit), they say that testing has become very difficult and thus they developed a new test methodology based on the dSpace product that gives the possibility to do automated testing of the components interaction and to reliably reproduce the failing tests.
Pretty interesting stuff but how does this relate to our adventure? It does because the document gives also some information about the can bus of the Vectra and has a picture of its topology. There are three busses in the car: low-speed, mid-speed and high-speed. This is the list of the ECUs for each bus:

• High-speed: Steering column integrated module, Yaw rate sensor, Electronic stability program, electro-hydraulic power steering, Automatic headlamp control, Automatic transmission control, Engine ECU

• Low-speed: Steering column integrated module, Body control module, Driver door module, Instrument panel cluster, Rear electronics central module, Shift lever module, Displays, Auxiliary heater, Passenger door module, Driver seat module, Parking assistant, Airbag, Sun roof module, Underhood electronics, Display module

• Mid-speed: Display module, Audio system, Car phone, CD changer, Electronic climate control, Global Positioning System, Navigation control unit, Telematics system

From this picture and list, we can deduce that two modules are acting as gateways between the different busses. They are the Display Module and Steering column integrated module. What they are exactly and what is their function, we don't know yet. I start now to wonder to which bus the can bus pins on the EOBD connector are attached. We will need more information on this and probably also to measure the speed of the canbus we have access to.