@Rosie For me, the interesting thing about that Vinaya story is that it reflects a situation in which a monastic manifesting attributes of the other gender did not create big problems or fusses, the response is smooth: okay, then live with that other community and follow their rules. Although, as you say, all this is still gender-binary.
Sadly, the tradition has not always been as cool as in that example. The Vinaya also bans ‘paṇḍakas’ (what we might call ‘queens’ today) from ordaining, after a story of self-advertising promiscuity; as well as ‘ubhatobyañjanakas’ (hermaphrodites, maybe transgenders). I think those in Thailand who argue against ordaining transgenders and gays equate either of these categories with the Thai term ‘kathoey’, ladyboy.
Jose Cabezón edited a good book entitled “Buddhism, sexuality and gender”.
@Vimala I attach an essay with quite a lot of bibliography and some analysis on the ‘paṇḍaka’ problem. Don’t judge too hard, it was my second essay for uni 
Essay on homosexuality - Bernat Font.pdf (120.3 KB)