"Ctrl" and "=" and "Ctrl" and "-" if I remember correctly
When moving you will just cycle the cabs without control transferring to them (this includes if you have say 2x166's on the Oxford/Paddington route you will move through 4 cabs.
When stationery, control will transfer to that cab, so, if changing ends you need to be not moving at the time (makes sense really) - it will then default things like the reverser to its default position etc fr the new cab