Yup we import Coal but Coal is not costly as diesel am i right? :D and also we do also have some coal In india and Regarding Copper & Aluminium wires which you are talking the reason to use Copper not only limited for higher rating of Current the reason is Aluminium wires form Sag in winter seasons which results in Cable to buldge downwards due to its weight and pressure due to which problems arrise for smooth running of pantograph over the wire. And also you might have seen some loads have been connected for Wires near some poles Instead Using Cu wires over aluminium as Cu wire also come accross expansion and contraction same like Rail lines when change in temperatures so to balance their Expansion & Contractions these loads has been hanged and EHV Transmission line have Aluminium i think in india due to Cost...
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Impact but if you go US or saudi arabia or some countries they even use Cu Wires For Transmission lines for Good Efficiency.
Now coming to your Dept Expenses and Wages if you think this way over any Improvements in latest technologuy in Railways or in any field then today whole IR would be on Steam Engines not even on Deisel Also i agree Deisel Engines need less maintenance then steam Engines but Their comes new provisions over new Technology and new things under use so those things need to be considered with cost impact.
Regarding Regular Cut and prune of trees it comes in Maintenance and for proper & Safe Run of trains through the section they will cut the only small amount+ 1.5 to 2 meter extra for considering abnormal natural situations like heavy winds storms where trees which coming near to contact with OHE. you have So many highways pasing through Forests so those cant be the loss for forests?And also Plans to Enhance the lanes for them their wouldnt come Ecology disturbance and Cutting of trees only when Railways do Everybody open eyes this is what going on. Okay Now konkan Passing through Dense forests so do you say its not good to elctrify Konkan route due to all this things wht i found in your comment?