I'm not sure about the C class, but there was a huge recall of E class w212 models over the ABS pump / braking system, basically the pump could fail catastrophically and render the car with NO brakes. If they haven't abandoned the silly/unsafe electric over hydraulic full authority control methodology for the braking system then you can't rule out remote controlled brakes.

Without regard to whether Hastings' car had the flawed ABS system (probably not). The very definition of an ABS system is that braking control is taken from the driver and given to a computer, so no the brakes are not immune to hacking, no matter how unlikely you think that scenario is.

I'll let Mercedes speak for themselves as to whether electronic control of steering is possible: http://techcenter.mercedes-benz.com/_en/distronic_plus_steer...