Ok here's some tips:
1. It's a good idea to drive the vehicle when the "Cleaning Exhaust Filter" message pops up for 7-10 miles to allow a complete regen.
2. When the "Drive to Clean Exhaust Filter" message pops up it is required to drive the truck until the message goes away. This message comes on when step 1 is ignored and the DPF is getting full.
3. Does anyone in your fire dept are aware of the regen process?
Not following the above will result in a clogged DPF and will require a trip to the dealer to initiate regen.
One thing you may check into there is suppose to be a (OCR) Operator Commanded Regen feature on some trucks that idle a lot. You may want to check into that feature, which will probably address your fire dept. issue.