Cab signals or lack thereof would not have been a problem. EL power running on the New Haven was done occasionally, on the rare side. One story is that EL power was loaned to the New Haven for use only from Maybrook to Cedar Hill and return. One day an EL bigwig was in Springfield, Mass. waiting for a train and watched in amazement as a pair of EL units rolled across the B&A diamonds onto the B&M tracks with a Cedar Hill/Springfield job. The power-hungry New Haven engine dispatcher used what was available. And thus ended EL loaning units to the New Haven.
The Lehigh & Hudson River had a special nuclear reactor shipment for either Electric Boat Company or the Navy Sub Base at Groton, Connecticut. L&HR power all the way. The L&HR had a trainmaster ride with the engines to ensure they were promptly returned without any side trips.
Never heard of Burlington Northern units making it to Cedar Hill, though. PRR sharks, maybe.
Ex-NYNH&H SS Opr