I personally try to refrain from putting Chi-Sau into a Sparring catagory, mainly because Chi-Sau in most cases starts from a point of contact and remains in a point of contact.
Sparring on the other hand begins from no contact and deals with many different ranges, with those ranges constantly changing throughout the exercise.
Both forms of practice are great tools for honing the skills, but neither can be classed as real fighting in my opinion.
Jin-Ka