Are they not insect-pollinated? If so, the main thing will be how many insects are on the wing.
There are a small number of papers published online, covering VERY few species, that suggest that self-polination is rare, but otherwise pollination is not inhibited (implying that hybridisation is possible).
Maybe test the possibility by using a brush on just one or two marked flowers to transfer pollen between the two?
What species are involved in commercial varieties?