There's a bit of a debate at the moment over electrifying the GWR route. The good burgers of Bath don't want those nasty overhead 25kv wires strung up through their city. Network Rail say that it's not possible to have a mix of third rail and overhead although they seem to forget that that's how Eurostar operated for years.
Now then, once upon a time the Swiss operated a three-phase overhead system. It must have made junctions very complicated!
Terry