This is a cross that I know very well in the nature. In the place where this hybrid was described, when N. cantabricus have the ovary closed by their own species, Narcissus triandrus subsp. pallidulus starting to bloom and the first plants in bloom receive the pollen from the late N. cantabricus. The result is a plant that contains most of DNA of N. triandrus subsp. pallidulus, and they are usually solitary plants, tall, like N. triandrus, with 1 to 3 flowers per escape (at least) with a nice scent. There is another nothovariety when N. cantabricus acts as mother, in southern Spain. They are big clumps with plants usually with one flower per escape or rarely two, I have seen 100 flowers in the same clump. This is possible because it has inherited the vegetative division capacity that N. cantabricus has..
I am still researching about it, but I think that if you cross both nothovarieties you will have in the next generations, fertile plants. This is happening in the nature with several narcissus.