As far as railroads being suburban and rural people movers goes: If I had a dollar for every foot of track which has been torn out since the federal government embarked on their big highway building campaigns, I'd be a very rich man.
That in a nutshell is what killed the railroad as a people mover in the less densely populated areas of the country.
Given the current emission regulations in place for diesel locomotives, it makes zero sense to examine anything but electricity as a locomotion power source. But that depends on WHY alternatives are being considered, not just the alternatives themselves. Is there a sufficient cost benefit per unit ton of fuel burned that railroads are seriously considering coal as a power source?