The Sprinters already do have hazard cams mounted on the dashboard looking out the engineer's window.
See the little white thing just to the right of the center divider on the window glass, framed by the windshield wipers. That provides constant live-downloadable video feed of the engineer's forward field of vision.
This I guess is just spying on the actual engineer with an extra cam on the rear wall of the cab. Engineers union is going to fight that one reaaaaaaallly hard. If they want to prevent them from texting while driving they tighten the regs for turning in all electronic devices before leaving crew quarters. I'm not sure this is going to do anything but make them really uncomfortable, distracted that the boss is looking over their shoulder, afraid to scratch certain bodily places that may get itchy sitting down for hours at a time, etc. There aren't many workplaces where that kind of scrutiny improves morale, productivity, or concentration.