I've searched on forum and didn't find anyone done it, just suggestions to put aftermarket ones, as oem would be very expensive and probably hard to do.
I Got 08reg and have another one 06 which I'm planning to sell and which got factory sensors. First of all I pulled out drivers side rear light on both vans and found additional harness on 06 going down for sensors, on my 08 wasn't. Then took off interior windscreen trim and just counted how many wires coming down on both vans. It was 44 on both. decided to unbolt 08reg ply lining and found hidden harness for sensors. took out cluster and found plugs for speaker and module. swapped everything, and activated with IDS, and it works!!! dindn't need any fuses or relays. Don't know if it matters but my 08 van got pretty much everything, factory heated screen, auto lights/wipers, power windows, alarm. Recently fitted cruise control and level2 cluster with trip computer and outside temp sensor.