Yes, in principle. You would need to use a dedicated SPI channel. The SPI pins on the expansion port could be used if you had no SPI temperature sensors, no external SD card (the internal one doesn't use SPI), and if using a Duet Maestro, no 12864 display.
In the firmware, the step interrupt handler (in file DDA.cpp) would need to be modified to send commands to the DAC instead of step pulses to motor drivers.
Unless the XY movement is linear with the output of the DAC, you would also need to add a new kinematics class to do the coordinate transformation.