Re Transport Canada's stress recorders on their flight check aircraft: A number of years ago they lost a flight check King Air when the wing fell off, so they are rightly concerned with structural fatigue.
AS far as the economics of new aircraft for contract firefighting and use of contractors vice government owned assets you can probably go through the arguments on both sides yourself. Doubt that the Forest Service has the cash at any one time to put on a contract to pay for new aircraft, and since they are specialist aircraft that can not be easily converted into hauling passengers or freight and after being fatigued and worked they have no residual economic value beyond $.10/pound the companies have no economic incentive either. Makes it hard to justify new aircraft.
There have to be bags and bags of old C-130s in various boneyards that have lots of airframe life remaining that could be economically converted and operated for a few seasons each, use up their remaining airframe hours before their date with the smelter. Would old Nord 262s, Shorts, and other over the hill passenger and cargo aircraft be useful? Not the FEDEX fleet of Flacons, of course.