The women at that company ought to walk out. The recidivism rate for “transgender” people is surprisingly high. This guy might very well “change back”, and then all those women will have to live with a heterosexual man they aren’t married to knowing intimate information about them.
Yes, it puts the company owner between a rock and a hard place, but the company will likely end up having to shut down anyway after the judgement and bad publicity; they might as well be able to blame the guy directly rather than some impersonal court decision.
A lot of transdressers still have not only the parts they were born with, but the drive that goes with them. Letting those mental cases in the restroom with women poses direct risk to the women. I would refuse to use a restroom that he was occupying. If there was only one restroom available to female employees where I worked, the atmosphere could get a little thorny in that company. I will only tolerate so much abuse and a homo/trans/whatever peeing in the stall next to me is going too far. No job is worth risking my personal safety.