The key point here is improving. For example, the doodad the BBC is marketing here is clearly not an improvement, is it? It's much more costly than traditional electrical rail (solar panels are much more expensive to maintain than a pole with a wire), it requires massive new infrastructure (the railway company would have to create a whole solar energy management division), and the only benefit is that it allows the railway company to avoid dealing with the regular electrical grid that powers everything else - for no clear reason.