BM&LP, like Muskingum Electric and several other electric lines, was an isolated or single-purpose industrial line that was mainly a case of "burn what you haul." Moving coal in an isolated loop operation, especially to serve a power plant that burns coal, is an ideal case for an electric railroad using low-cost, low-speed HV traction, as long as the equipment is available pretty much off the shelf as it was in the 1950s and 60s (when PRR was buying E44s and the like as basically electric conversions of diesels). Bears little relevance to main-line operation, then or now.