Branson uses a fully mechanical engine, instead of the computer controlled ones like other brands.
The way they used handle the exhaust aftertreatment is with a bolt on DOC and a datalogger. All it took, was to gut the DOC or replace it with a muffler and unplug the datalogger. In the end, you had a perfectly running tractor with a simpler muffler.
On the newer models, they use a DPF, datalogger and a butterfly valve on the exhaust, pretty much like an exhaust brake, but it's used to increase the temps on the DPF for the regen process. It's still a mechanical engine and while I haven't seen one in person, I'm pretty sure it's a bolt on deal as well that can also "fly off" if needed.