Not in the way you think............. I run Two Servos, from an ADC DL06 and the modbus controls them, but they are not integrated with Machs motion planner at all. I use them to run an ATC. You can send movement values to a register in a CTRIO module (one CTRIO module will control ONE Stepper or Servo that the drive will take Step and direction. The down side is you will have to track absolute since the CTRIO only does incremental.
I use mine for my Read-a-head swap-arm ATC, This gets tool changes down to about 2-3 seconds, also buy having intellegent IO like a PLC, you can move all your M6 processes to it and it will handle the tool change. I.e. you send out a tool change command, and what tool, the PLC does the rest, once the initial tool is changed, It sends an Im done to mach, mach will continue machining, meanwhile the PLC rotates to the next tool and gets it independant of mach.
You cant do that if you use one of your motion axis for your ATC since Mach will tie up until that axis is done.
Unless, high end top speed ATC is a absoulte priority for you, it is much, much, much easier just to run the ATC as an Axis, and do a traditional simple rotary axis.
Scott