At 163,000 + miles my Ford Ranger is pre-DPF but does have an Oxidation Cat fitted from new. If you drive like I do, gently, then the Cat gets bunged up and MPG worsens by about 0.5 mpg per tank of fuel. I do a 50 mile round trip every month for some far flung customers and once suitably warm I get it to around 4,000 rpm steady for a couple of miles. A fair amount of black smoke is produced as the Cat cleans itself but once finished it will emit no visible smoke whatsoever. If my low tech, IDI engine will pass without any trouble I'm sure the newer trucks and vans shouldn't have any problem at all - assuming your MOT tester has a brain and is actually capable of using it.
As earlier said the new rules seemed aimed at removal of the modified diesels with DPF's removed and mapped out. Technically you haven't actually needed a working DPF before -only evidence that it's present was needed to pass the MOT.
Now they do seem interested in Particulate Emission, if your vehicle had a DPF from new it has to work or it won't pass the test but commercial pick up of DPF's is way behind the car world. The Ranger didn't get one until after 2012 but my trusty 406 had one from 1999.
As an aside there are now a tremendous amount of modded diesels on the open market at very low prices and they don't seem to be selling. Who could possibly have seen that coming
. 300+ bhp straight six BMW's and V6 Mercedes are now available at bargain prices for anyone who doesn't live in a City and is feeling brave.