Just done a test in Cumberland Yard using four locos. Using Geloxo's excellent table, I configured the first two locos as a leading group and the rear two as a banking group (with imaginary wagons between the groups). The brakes worked correctly in all locos and all locos provided power. I was able to use Ctrl+ to toggle between the cabs of a group and Ctrl- to toggle between groups. So could check events in every cab. In the Fully Fuelled scenario, you have to attach a pair of locos to the back of a train to act as bankers. There is already a pair of locos at the front. Unfortunately, Ctrl- doesn't seem to work in this scenario so can only use Ctrl+ to toggle between cabs within whichever group you happen to be in. Only way to move between groups seems to be to run the half mile length of the train. I guess this is a bug in the scenario.