As per my experience you can hook it up. Ofcourse you will not get the good result with your 48 volt motor with 24 volts.
Spindle control is accomplished in the 24 volt system by the front end adapter, much like the Shield is the controller for the stepper motors.
According to me 48 volt supply would need the same type of device to use programmatic spindle control.
Uh hungh. Like.