I actually don't believe the narrative that there are trans women attacking women in bathrooms and SA'ing them. I'd like someone to give me evidence of it occurring at any rate to warrant the discrimination that occurs.
There's a massive mall near where I live (in a major, metro area) and they have a gender-free bathroom. All folks use the bathroom- the doors go right to the floor and ceiling, but the hand washing is co-ed. And I've never ever heard of anyone getting attacked in that environment. So I find it extremely hard to believe there's any evidence to support it happening on a smaller level involving trans folks.