Many of the smaller railroads treated their own ties my just soaking them in oils and tar. It was not till later years that they were put in the long pipes and had all their moisture sucked out and then presure treated with creosote chemicals pressed back in, at big tie treating yards and businesses.
I saw the soaking tank at Piney River, VA in 1962 on the Virginia Blue Ridge RR as one example.
I am sure the EBT used ties from Mt. Union's treating plant, even it they were the rejects that did not pass the tough PRR inspection. That would be the ties even below the "yard tie" class. I do not know for a real fact that the EBT used treated ties, but I sure think they would have had a great benefit doing so, and we do know they used standard gauge length of 8.5' ties on the main line.