I'd just like to make some points without really coming down on one side. From a technical perspective, I'll say driverless trains are reasonably interesting, but that's just coming from the geek in me, trying to figure out how to make them work, rather than actually feeling like they should be implemented.
1. Purpose of "Driverless" trains:
The thing is, with ERTMS and ATO, the major benefits of automation will have been achieved. Those being increased capacity, shorter headways, operational/energy efficiency improvements and speed increases. The only "saving" that I can see would be not having a driver, but instead having a more expensive guard-driver hybrid. On DOO lines (which are increasing in number) this would make train operation more expensive.
This is different from cars, whereby full automation would have HUGE safety implications, because a car can be told to stop on a sixpence and get out of the way easily. If a machine can figure out well enough when to do it, it's better than a person. ATO in trains already does this as much as is feasible given the limitations of trains. The person's job is about the human interaction and dealing with faults/problems/unprogrammed inputs.
2. Technical Barriers
I see these more as hills. They're can all be climbed, just some are steeper/taller than others and over time, they get weathered down to small mounds. If there's a genuine need for "driverless" trains, we'll figure out how to do it. If we can split the atom* and go to the moon, we can get trains to drive themselves...............
3. How the economy/job markets work
I've seen a lot of "everything will be automatic and no one will have a job anymore" posts. As a professional software developer, I would suggest that the more things are automated, the more software will need to be written to automate them, the more people will be hired to write the software/make collisions detectors, write increasingly complex laws to give machines rights, fight in the inevitable cylon uprising...............
* We can split protons now too, how cool is that!!!!!