We have guys working in ND, SD, AK, Canada, Arctic Circle and WY that have all found out DPF does freeze. BUT, we have not had an issue other than needing to buy another jug or two (or 40 in one case, pallet left out at -40+). Where our guys work they generally keep a jug or two extra in their trucks. In the winter they haul it into the camper when they get setup. You only forget it once at -40F because the jug will burst and you'll be smelling it for months. In the tank is no problem unless it’s so cold you jell up with the motor running (seen it) but by then your stranded anyhow.
All our trucks have welding blankets, gas gen sets, deep cycle battery banks and torpedo heaters to get you thawed out when hell freezes over and your 100+ miles from anything.
Short and simple, most don’t have to worry about DPF.