Transparency Issues with ACEA Agreement?

So while voluntary agreements to reduce CO2 emissions from motor vehicles may be a good thing, how does one make sure that the actions taken by the OEMs are sound? WRI asks this question in their recent report titled Transparency Issues with ACEA Agreement: Are investors driving blindly?. You might remember the WRI-SAM report called Changing Drivers, which at least I take seriously in spite of simplistic nature of that report.