Hi Juan, CNC machines are usually used for moving a tool using multiple axes in a coordinated way. If you want to do the same with a PLC, the program gets very complicated and that's why it does not make sense to use a PLC instead of a CNC machine.
PLCs are usually used BEHIND the CNC for controlling more PLC like functions for the machine such as hydraulics,clamps, etc. So the CNC does the more complicated moving stuff but the PLC controls the general functions of the machine in the "back end". That being said, CNC's and PLC's are two different tools that are used for two different jobs.
As far as I know, it's not common to translate G codes to the programming languages that can be used for PLCs because as I said if you want to write the same codes for motion control using a PLC, it would be very complicated and in most cases it will not function as good as a CNC.