It depends on whether they are determined to be at fault - if so, they are fired.
I know one driver who wrecked a truck, when dispatch called shortly after a pickup, asking for info on the BOL. Driver reached for it, taking eyes off road, then saw the truck heading towards the shoulder [the hand always follows the eye!], over corrected, and laid the truck down. No other damage, but the driver was fired within the hour.
Judging by the "John Doe" accident scenarios posted by CCJ, the driver is always at fault - even when a 4 wheeler does something totally unexpected & illegal.