Here are some details that I find telling, from the Montana FWP EIS:

--33 miles of stream involved
--Yellowstone cutthroat genetics are 99.5% pure (.1% rainbow trout, .4% westslope cutthroat) and there is a fish barrier in place downstream to prevent further rainbow introgression.
--Brook trout are already under must-kill regs. I've seen a grand total of two (and they swam towards the light).
--Last year, MT FWP and YNP combined to shock and remove only 102 brook trout (from the entire 33 miles of stream), including only 7 young of the year. The peak year for brook trout removal was 2005, with only 1104 removed. A grand total of 2,608 brook trout have been removed. They have not been able to find more than 200 per year since 2006.