you cant ask the driver of a modern freight train to do similar with a bucket of diesel followed by a lighted match to burn off the vegetation but you could employ gangs spraying a glyphosate weedkiller to kill the vegetation instead but then that costs.
But 'vegetation' in general is not a problem is it? Trees, specifically, are as they are tall which means they could block the line if they fall and there may also be more 'leverage' in play in high winds which could make them more likely to fall over. The only thing you'd want to use weedkiller on is invasive species like Japanese Knotweed. My view is that any trees far enough away that they can't fall on the line should be left alone, but I can see a case for felling trees that could fall on the line. Once the risky trees are gone, allow brambles, hedging plants etc. to grow back on the linesides and keep and eye out for anything growing too tall and cut it back or root it out to ensure it can't fall on the line. Removing tall trees near the line but allowing short hedges eliminates the risk of falling trees and may reduce leaves on the line (falling from a lower height means they have less time airborne to reach the track) while still providing a (different) wildlife habitat, unlike bare soil or short, frequently mowed, grass. Unlike a tree, which could destablise earthworks if it falls, a hedge might also help secure earthworks but I'm no expert.
