This was actually a government owned business that used the railway system to safely transport goods, it was never owned by the railroads, these signs were used from the 1940 to about the late 50s during the 1960s it was purchased by a private entity, they shortened the name to REA the company filed for bankruptcy shortly thereafter.
Here is a website that will give you some history.
http://nrhs1.org/images/e-Dispatcher_July_2014.pdf
