I hope the driver recovers - seems the circuit breaker may have come to his aid.
Unlikely, on its own, to do that - the trip current is (from memory) something like 400 A as a minimum, and protects the system not people. That is way above the trip current of ELCBs (30 mA) in your home, which are there to prevent electrocution. And, of course, with the traction current return via the ground, earth leakage detection is not possible.
However, one of the factors that determines that trip current is the maximum voltage on earthed metalwork under fault conditions ("fault" in this context means a short circuit, usually to earth). That induced voltage is only there for a fraction of a second, until the breaker opens. I'm not sure what the limit is now, it used to be 430 V. So that's what is likely to have happened - if you are close enough to a flashover or contact from the overhead wiring to the track or train, you may still suffer injury.