Curious to know what does the diesel PM have for their diesel exhaust/scrubbing system? Is it similar?
It is very similar. ALL of the new "clean diesel" emission control systems are very similar. Doesn't matter VW or Mercedes or BMW or Ram or Ford or GM.
They all have an EGR system (some have both a high-pressure and a low-pressure EGR system - notably VW), various "throttles" in the intake system and "back-pressure flapper valves" in the exhaust system to produce the correct amount of EGR flow, an oxidizing catalyst, a diesel particulate filter (often in the same housing as the oxidizing catalyst), a SCR (selective catalytic reduction) catalyst, and the "diesel exhaust fluid" tank, dosing pump, heating elements to stop the DEF system from freezing, level sensors, etc.
The early VW "clean diesel" TDI did not have the SCR/DEF system because in a VW Golf sized car they were able to squeak through the emission regulations without it, but the newer models have switched over to use it.
The other common thread is that, to my knowledge, all of the "clean diesel" engine manufacturers have been having all sorts of issues with them (although the particular issues vary between manufacturers), and they are all expensive to keep running out of warranty after things start failing.
Friend of mine has a 2010 Golf TDI and it needed the DPF replaced before 100,000 km (thankfully under warranty) and it has gone through several exhaust back-pressure flaps.
A friend of mine is a heavy-truck mechanic ... they're having trouble, also. Down-time is much, much higher with the newer trucks (and if the wheels aren't turning, you aren't earning). Many fleets have been trying to keep the older trucks on the road as long as they can, but with the mileage many of these trucks pile on, that can only be done up to a certain time before the older trucks are beyond repair.
I think the "clean diesel" emission control systems were forced onto the marketplace by the emission regulations before the technology was ready for prime time.
I was a long-term VW TDI diesel owner, but I've switched back to petrol power for the moment until the diesel tech gets sorted out and becomes proven in the long term.
Mercedes is by no means alone in having these problems. The North-American-spec "clean diesel" Fiat engine in the ProMaster hasn't been around long enough to know how it will be in the long term. An ominous indicator is its use of a Bosch CP4.1 injector pump. That pump has been a disaster in the VW clean diesels. I will not buy a diesel engine that has a Bosch CP4 injector pump. Some imaginative folks have developed a retrofit kit for the VW clean diesels to allow the previous-generation, more expensive, but more durable, Bosch CP3 injector pump to be fitted to those engines.