Seems like this is well covered by now, but I'll throw in my two cents -
said, if the light comes back on, take it to VW. Don't just stop at getting the code readout and report, get a full estimate for repair also.
2. Then go to the Ford dealer, and show them the estimate and report. If the selling dealer is responsible for the repair, and the repair is covered under warranty, there should be nothing preventing the Ford dealer from contracting the repair to VW - press them to do exactly this. The money passes through the Ford dealer to VW - Ford isn't going to make a dime on a warranty repair anyway. They have plenty of Fords to repair as it is.
The reasoning is, VW Touareg TDIs are special beasts. I would not trust a non-VW dealer to repair a VW vehicle, least of all one that's designed by VW's master engineers to fool regulatory agencies worldwide. That, and a VW dealer will have the experience to complete the repair (certainly a Sydney VW dealer has done many such repairs by now) and the correct diagnostic equipment to validate the fix, probably with a lower chance of screwing something else up in the process. Clearly your Ford dealer doesn't want to be in the business of fixing your VW over and over, and neither do you want to see the Ford service manager more than you see your new Touareg.
At the very least, find a good independent VW mechanic who has experience working on the 3.0L TDI and strongly encourage the Ford dealer contract out to them.
They're great vehicles, and hopefully you've seen the last of this particular issue. My 2010 Touareg has been a trustworthy Sherpa, always ready when I need it and totally reliable - I hope the rest of your ownership experience is similarly enjoyable.