That's why I'm thinking it's up to cis people to make the bureaucracy impossible. They'd need to implement and maintain a record of all employees - cis and trans alike - who have publicy outed their own gender-reassignment statuses. Doing it for trans people alone would be indirect discrimination.

(Also, trawling individual employees' public actions, such as personal social media, would only be acceptable if it was applied to all employees?)

My first thought with this is that ungovernability is the response to this while also demanding strict compliance from them as data handlers and employers.