They would also allow 95% of a route to be electrified, leaving tunnels and sections under pedestrian and other bridges un-electrified and covered by small capa

They would also allow 95% of a route to be electrified, leaving tunnels and sections under pedestrian and other bridges un-electrified and covered by small capacity batteries. Especially since the train is unlikely to be accelerating during those sections. When Network Rail in the UK looked at electrifying the Great Western Mainline, the majority of the cost is actually in a very small % of track length which is where the line goes through Victorian tunnels and under old bridges. If your battery only needs to be sized to maintain speed for sections a few miles long at the most, you can get away with much smaller batteries. I know they are running trials of what are effectively "tri-mode" trains already which are diesel/battery/OHL.