I have also received traffic on this frequency today and can confirm it is Missoula County Fire/EMS dispatch, transmitting on 151.340. It appears to be a rural fire district possibly Frenchtown. I will continue to monitor it for further details and specifics.
Just checked my radio and found that this is known as Fire channel 5 in Missoula county. Since I have been in the Bitterroot i have kinda forgotten the areas covered from 1-5... but 1 is south Missoula/Lolo, 2 is central Missoula, 4 is north Missoula county if i am rember properly.
hope this helps