There's probably no right answer to this question anyway, since I'm sure some trans people give blood without telling their status while others are turned away if it's known. Might depend on the views of the person drawing the blood. It's all hypocritical anyway; during blood drives at my high school, I was barred from donating since I had sex with men (dangerous lifestyle, rabble rabble), while all the straight kids who had had plenty of partners (many of them overlapping actually) were okay for donating. If they don't want my blood, they won't get it. It's a shame, since it hurts lots of people who need it.
Lia