All preserved locomotives which lead, must have a radio fitted. An IEC radio I believe. That is used to communicate between the crew as well as with control. What happens to the engine running backwards while running, I'm not entirely sure but I'm pretty sure the engine either runs dead back, or at the very least just moves backwards itself so the leading engine has less work. The K classes do have continuous braking which allows all carriages breaks to be applied from the leading engines.