The Captain will tell the handler which bits they wish to be de-iced, and it is interesting how this can vary from Captain to Captain.
I was always a tad concerned that the pilots of a European based CRJ operator at a well known regional apt in uk with a shortish runway, regularly refused de-icing when all the other night stoppers had deemed it necessary. On a couple of occassions my guys sprayed the a/c anyway because they could see that there was considerable coverage of frost/ice and they were unhappy to let it go. The airline was billed but argued about paying claiming that the handler had 'no right' to spray unless their crews authorised it.
It always struck me as a false economy as the cost of an accident is far higher.