I thought the 3 BFOs (last Mk 3 stock built?) were intended for the Manchester business peak services that replaced the 1966 Manchester Pullman stock (vacuum braked to the end).
Regarding locos away from the wires, a good proportion of the Class 86 were built at Doncaster, well away from any wires at the time, and I can recall one in what I presume was 1966 sat brand new in a bay road at York, presumable on a delivery run. Likewise, all the EMUs around Liverpool and Manchester at the time, 3rd rail and overhead, were overhauled at Horwich Works, well off any electric system, which towards its end became its principal activity. They all ended up with common standards of interior paint and upholstery. They were hauled to/fro by diesels.