Makes it even crazier that Bart would choose a non-standard gauge 75 years later. And now they're stuck paying for custom trains with less flexibility and longer lead times.
I also don't know where you're getting 125kV from. Many trains throughout the world use 25kV, especially high-speed ones (actually high speed, like 200+km/h), but BART uses 1000V, which is closer to a typical subway system.