The major problem with using reciprocating steam locomotives (and the main reason why most railroads stopped using them) is the expense of maintaining them, not operating them. While Norfolk & Western and a number of other operators in the U.S. and abroad (not to mention innovators like Porta) did a great deal to improve the overall efficiency of steam locomotives and did make improvements in locomotive servicing practices, steam locomotives remained (and still remain) very labor-intensive machines in terms of maintenance. Sure, coal may be cheaper, but no railroad will use locomotives that are far more expensive to maintain than the diesel-electric locomotives they've already got (especially with labor caosts being so expensive these days).