In the German car press, several news articles have been published about the ongoing Dieselgate-related investigation into the Opel Zafira 1.6 Diesel (and to a lesser extend the Astra Diesel).

AutoBild
Automobilwoche

AutoBild has some details about the ALLEGED findings

Now my German is hardly perfect, but I tried te summarise the basics in the AutoBild article:
* A hacker by the name of Felix Domke has been digging into the engine management software. His findings show similar functions as the ones VW used. The software that regulates the emission control only functions under VERY specific metrics. The software does work in circumstances similar to lab tests.
* Opel is said to turn OFF the emission controls:
Above 2400 revs
Above 1000m (due to the low air pressure)
Above 140 km/h
under 17 degrees and above 33 degrees Celsius outside temperature
Especially the rev limit and the outside temperature leaves lots of times when the emission controls don't work, is the implication.
* Cutting off emission controls is allowed in the EU under certain circumstances where the engine needs to be protected. The parameters that Opel has set seem to be way too strict and smells of manipulation, according to the ARD (TV) and Spiegel magazine.
* Opel denies vehemently that it uses software that can sense of the car is in test lab. And it says that the complex interactions within the emission control software have been misinterpreted.
* The German Transport Ministry is looking into documents requested from Opel to see if laws have been broken
* The same ministry is also looking into VW (obviously) and Fiat. Opel is the third party to be investigated.
* A more local authority (Landgericht Darmstadt) is looking into Opel's advertising for the Zafira, claiming very low pollution.

At least, that's how I understood it :-)

The short version:
The issue seems to be that Opel uses very odd parameters to turn off the emission control software. Which means that most of the time the car is polluting way more than the Euro-6 Diesel permits. The question is if this is all within the law.