Rail lines that have too little traffic to be electrified may face difficulty in adapting the propulsion of their moving railway material to the progressively more stringent regulations on gas emissions. Lasting changes in the relative prices of fuels also affect which types of fuels and engines are most cost-effective. Here we will attempt to establish the bases for evaluating whether the current Diesel-Electric paradigm is becoming outdated, and whether one particular alternative, a gas turbine fuelled by natural gas, is worth switching to. We will be focusing on the specific example of the Lleida-La Pobla rail line, and whether the industrial tissue around it is equipped to facilitate such a change.