Back in 1987 I was offered a job with the Union Pacific Railroad in Omaha as a Radio Technician. They wanted technicians to have a General Radiotelephone Operators License and be a Certified Electronics Technician.
I have the GROL and they would pay me to take the CET test.
I don't know what the requirements are now because I turned down the offer.
What you might want to do is inquire, with the Railroads you are interested in, what they require for the position. Also some roads use state employment agencies for hiring, check with them too.
Good Luck!
Regards
Michael