We don't have to ensure that. If a woman has masculinised herself sufficiently so as to be causing alarm in a woman's bathroom it is entirely appropriate to exclude her. That is part of the judgment. It was something I did not see coming, but it's there in black and white.
The judgment went on to say that the transman was still not legally permitted to go into the men's bathroom, so there was a danger that she (and I think also extremely feminised men) might have nowhere to go, which was also unacceptable. They recommended that service providers consider making more single-occupancy unisex facilities available for this eventuality.
Of course the judges could not say that such women are legally permitted in the men's room. But we can all see the obvious, practical solution. If the woman is so masculinised that other women code her as male, she will attract no remark whatsoever in the men's room so long as she simply goes into the cubicle, comes out, washes her hands and leaves, without looking at anyone or speaking. Which appears to be normal, accepted behaviour in the men's room.
One might also suggest that such women can use the disabled toilet. There are very few of them, and most disabled toilets are empty most of the time anyway. But in practice, even though she isn't legally allowed in the men's, she can obviously go there. It's what she wants, so her best course of action is simply to do that and say nothing about it.
The judgment makes it entirely clear that a woman who objects to Buck Angel in the women's room is in the right.
