While one could argue that the use depicted in the photograph is not specifically prohibited if it is not distracting the operator most carriers simply ban the use of various devices in the cab while in operation. One might consider that this photograph is not setting a good example.

§ 220.303 General use of electronic devices.
A railroad operating employee shall not use an electronic device if that use would interfere with the employee's or another railroad operating employee's performance of safety-related duties. No individual in the cab of a controlling locomotive shall use an electronic device if that use would interfere with a railroad operating employee's performance of safety-related duties.