regardless, level crossings work perfectly well: they simply have a gap in the electrified rail over the crossing (and the train is longer than the gap)
if you look closely here you can see it: https://www.networkrail.co.uk/wp-content/uploads/2020/07/Ash...
One of the key drivers for cheaper and easier footbridges is to close level crossings. In the UK we have tons of crossings - footpath, private road, and highway - dating back to Victorian times, and Network Rail would like them gone. They're one of the biggest remaining sources of injuries and deaths on the network, especially on 125mph fast lines, and are operationally awkward.
They got rid of a bunch of private farm crossings during our Foot and Mouth Disease outbreak by going door to door with desperate farmers and offering wedges of cash to give up their private crossings. They care a lot.
A quick search on Google Scholar showed up this article on FRP footbridges, which mentions that the first FRP footbridge in the Netherlands was constructed in 1995.
https://www.sciencedirect.com/science/article/pii/S209580991...
A few minutes of googling gives me https://www.fibercore-europe.com/en/projects/, which has dozens of FRP bridges. I doubt that’s the only producer in the world. I don’t see what’s special about this one (but feel free to educate me)
That leaves the shape. I would guess the corners in the road are there to avoid having to use land that isn’t owned by the railway. If so, what’s left is the specific design. That’s nice, but other nice designs are possible.
Now, as to the idea of making a pedestrian bridge over a railway: it’s better than no pedestrian connection, but the stairs on such bridges necessarily are fairly high. Train tracks often lie above ground level, and even if they don’t, the total height to the top of the overhead line, plus some safety, plus the height of the bridge’s deck means you’re easily going two floors up and down.