Soldato
It's only a visual inspection to start with so lots of companys now cut them in half, gut them and reweld them back together so it looks like it's still fitted. However I'd guess, in the same way that they eventually brought in emissions testing for a diesel to test for your CAT's operation, they'll find a way to test a DPF somehow (even though it's not really an emissions thing).
So a visual inspection would not pick up a nice new weld around the box?