So I have taken from the Manual of FSDT LSZH. I made a picture. To me it makes the impression that the defrosting will take place at the original locations. Is also seen in the picture like that.
But you posted in the GSX section! So I thought you were asking something about the GSX deicers. If your question was about FSDT Zurich, you should have made it more clear (nowhere in your previous messages you mentioned Zurich).
Those in the picture are NOT the GSX deicers, they are the FSDT Zurich deicers. They are entirely unrelated to GSX, and have been in the scenery since it was released, long before GSX.
There's nothing you have to do to enable them, they just appear in that place, but only from December to February. And, they are just spraying, without any other simulation effect.