Do you know if the "particleboard" is oriented strand board (aka waferboard) or is particleboard. Also, is it a subfloor on the joists, or is it an underlayment. What is the thickness.
Particleboard is a very poor choice for a wet environment, and if that is what is installed, I would be inclined to pull it up and put down plywood. Particleboard is very inexpensive, and may be tempting to use for inappropriate applications. I would say that if this was a dry-room, no problem. If the particleboard is going to stay, I would install a ceramic or porcelein tile on a cement backerboard nailed into the particleboard. That should hold and deflect moisture. Using a 1/4" hardiebacker, I believe your tiles will be fine and under warranty since the underlayment would then comply.