IIRC, the driver is always liable for the vehicle being operated in an unsafe manner; if this is due to the vehicle systems being maintained in a condition that is unsafe, that's still the driver's responsibility.

If the unsafe condition of the vehicle resulted from a manufacturer's defect, this, again IIRC, generally allows those who experience damages to seek compensation from the manufacturer, but doesn't necessarily relieve the driver of liability (legal liability for any particular harm isn't necessarily exclusive in one party.)

For now, and at this level of automation (level 2) it is the drivers fault. When cars reach higher levels of automation (that generally means deciding more things like lane changes, target cruise speed, etc) it then becomes the car's fault and by extension the manufacturers.

Is that written, or just your opinion (professional or otherwise)?

For one, Volvo has decided to take responsibility for accidents that happen during Autopilot driving http://www.volvocars.com/intl/About/Our-Innovation-Brands/In...

That's what eg Google is lobbying for.

The driver, just as if they had set the cruise to 80 themselves.