I can't imagine a driver can see a great deal at 186mph through the front window of a Eurostar set and, even if he could, if you're close enough to see an obstruction on the line you're too close to stop. That deer the driver sees is going to get smeared down the train regardless of whether the driver is in control or a computer is.
Similarly, I (think) the Pendolinos are speed restricted when the in-cab signalling technology fails because it is understood the driver can't react to problems at full speed.
Anti-lock/anti-slip technology can deal with grip problems far quicker than a human can, as anyone who uses traction control or ABS on their road car will tell you.
I think many of the basic issues drivers deal with manually will be automated in the future, even on high speed trains. Computers can do it better and quicker than the human eye. Computers are less likely to go through red lights by mistake, or to be packing their bags instead of watching the track ahead.
But I can't see trains ever going fully automatic, at least not in my working lifetime. As with planes, I think the human desire to see a person at the front, as a failsafe, will override any economic arguments that can be made. A computer can't evacuate a crashed train, or set detonators on the track, or do any number of things you really need a person for.
For the same reason, I don't see the Tube ever going fully automatic. ATO is installed because you can run more trains automatically than you ever can using manual signalling. I can see the Tube heading towards the DLR model of having a passenger service agent. But I don't think people would ever want a tube train with no staff at all on board. For one thing, 7/7 and the vital role drivers took in that incident is still too fresh in the mind.