i've never had any success trying to print on fabric with a laser printer. i've tried both untreated fabric and fabric pretreated with Bubble Jet Set. the toner washed off every time.
if your printer is less than 2 years old, i don't think there's any harm in trying as long as you run your fabric through on the straight path (straight in one side, straight out the other, doesn't go through the roller and come out on top of the printer). technology changes all the time. maybe the newest toners will work?