For workplaces, trialling a policy where the unisex disabled toilet is used by a likely very small number of trans women or trans men seems very do-able?
For starters, HR know who works in a building, and what floors, and the number of those people who are wheelchair users or have a guide dog. They can check the toilet provision ratios. Obviously if someone hasn't declared a disability that'll be an unknown. So HR will need to be watchful for any unwanted consequences of the new policy.
It would mean that the Men's and Women's toilets are protected as single-sex spaces, and they can keep their cubicle door gaps. Which are so important for safety and well-being.
In the unlikely event a trans employee behaves badly, such as a dirty protest, there are already disciplinary processes. They could be suspended and lose their job. And no-one, even a captured Trade Union, is going to greatly sympathise with someone who trashes the disabled toilet. The optics are appalling.
So introducing a policy that trans employees (and visitors) use the unisex disabled toilet if they are uncomfortable using the communal toilet for their biological sex, seems sensible.
As I said in an earlier post if I used a wheelchair or had a guide dog I wouldn't like this at all. But, toilet refits are very expensive and difficult to justify for the likely small number of employees affected.
Public toilets are likely to be much trickier. Bad behaviour is much more common as a previous post noted. And much easier to escape being caught.