Railroads generally fill the transportation need for relatively low-value/high weight commodities such as minerals, oil, grains, chemicals, lumber, etc.  They haul little finished consumer products and food products.  Plus the loading/unloading expense for hauling relatively short distances would out weigh any gain from less fuel used.  
Perhaps a better way to reduce the impact of trucks would be to encourage regulations and industry incentives for converting more long haul trucking to CNG, compressed natural gas.
As long as we are surrounded by an ecosystem (very productive coniferous forest) that creates large amounts of combustible biomass, periodic large fires will continue to be (and always has been) part of it.