This report has some info about the trendy rollout of mixed sex toilets in Wales, the risks and practical implications: Mixed sex toilets in Wales' schools – breaking the law - Merched Cymru The quotes from teachers about the problems are really striking.
The argument is that open plan toilets with fully enclosed cubicles prevents bullying, but I've yet to see any research or evidence of this. I'd have thought it just pushes the bullying/ bad behaviour into the cubicles which are then impossible to supervise, as you can't even overhear what's going on in there.
Some more relevant links here:
Hygiene and health risks
Male toilets are dirtier than female toilets. Unisex toilets are worst of all:
Hospital toilets harbor multi-drug resistant "superbugs", study finds
Poorly ventilated toilets (such as those with full height doors...) have a higher cross infection risk
Public toilets with insufficient ventilation present high cross infection risk - PMC
Assault
Teenage boy arrested after girls 'sexually assaulted' in gender-neutral school toilets | UK | News | Express.co.uk
Man pulled woman into nightclub toilet cubicle and attempted to rape her - Wales Online
London: Predator, 24, raped 12-year-old in toilets at King Cross | News UK | Metro News
This attack was thwarted because a woman was alerted to a male voice. Which obviously wouldn't have raised alarm in a mixed sex toilet:
Man who 'hid in toilet cubicle' found guilty of sex attack on woman in Connah's Quay pub - North Wales Live
Medical emergencies:
I suspect that people die in toilets more often than we see reported, because who wants that to be the thing everyone knows about their loved one? Fully enclosed toilets are much much riskier, especially if the door opens inwards because you can't see someone, you can't speak to them and see if they respond, and you can't get help to them.
Woman lay dead in Blackpool restaurant toilet for two days - BBC News