Divvy, I have a happy story to do with TTTS, my SIL had this with her twins and didn't find out til quite late (can't remember exactly as it was 2 1/2 yrs ago now!) but both twins survived and although they were born 10wks early and one was quite sick, with one being 1.5kg and one only 0.5kg. They are both here now and going through the terrible twos, they are little tornados with their big brother.
I hope everything goes well for your friends, good luck to them.