In the UK, a recent Supreme Court decision has clarified that "sex" in this sort of context refers to biological sex, and is not affected by any shenanigans with birth certificate changes or GRCs.
Right. These guys are "biologically female" by that ruling. Do you think the people pushing these bathroom bills are going to be comfortable with them in the ladies room? I doubt it.
Ah, sorry, I misread your previous comment. And yes, the general gender-critical position is that transmen are welcome in women-only spaces, since they're women.
Though in practice I wouldn't be surprised if we eventually converge on "women only" and "unisex" as some sports have done. The risks posed by self-identification are very much one-way; this isn't a symmetrical situation.