Surely that's been the case ever since multiple units have existed?AIUI part of the some recent specs (might include the 800 series) is that a failed unit can be coupled to from either end by another, basic control provided over the connection wiring, and even if brakes etc need to be isolated and released on the failed unit, there is sufficent brake capability on the recovering unit that the combination can be taken to a point where it can be dumped out of the way, albeit at low speed. But it only works on like units. On a mixed route like the ECML we have many different fleets mixed up and no way to interwork, even for recovery.
You can run 2+x 14x/15xs together with the electrical boxes retracted to only provide mechanical rather than electrical coupling. As long as the coupler is the same type and at the same height, you can mechanically couple to clear the line?