That would be unrelated, GPUs use the ATI library and if the ATI library doesn't support something, that is ATI's fault.
The extra programs that allow you to avoid the ATI limitations indeed are custom and not OS independent, the ATI library is.

In cgminer I talk directly to the USB devices and can use any USB control necessary as required by the firmware
e.g. in the BitBurner we use control transfers to set and get the voltage and that's available via the API also at any time while cgminer is running

However, regarding cgminer support, I've no idea ... I'm awaiting a reply from Barntech