It's important to realise that often when you are talking to people about the NLRBE concept that you are answering a question based on a set of assumptions that are not relevant to the world of the NLRBE.
This question really is about ascertaining who will perform all the menial or unpleasant jobs that are currently covered by the existence of a low-waged working population. Further, the question really is "Why would anyone clean toilets by choice" and in the clarification of the question lies the seeds of the answer.
The truth is: Nobody. Nobody wants to clean a public toilet. Nobody wants the job of cleaning a stranger's excrement up after them! But what is also true is that we have technical ability to design toilets that are auto-cleaning for sure.
So the question really is: why do we currently have people doing that?
The answer is two-fold and both are heavily symptomatic of the current, money oriented system that we are living under.
For one thing, designing and rolling out automated toilet system to replace every public toilet currently in use is exceptionally expensive. The engineering, the materials, the maintenance (bear in mind also that a technical solution under the current system would be designed and built to a budget and so would inevitably require on-going maintenance which also adds to the cost). Contrast this to the relatively low-cost solution we have in having a poorly-paid human being to do the work. It's a no-brainer right?
The other reason is because if we automate all the public toilet cleaning, why stop there? Who is to say we can't automate ALL the other menial task the low-waged perform now? And if we do THAT what are all of these people going to do for work? How will they make money to then spend on other goods and services to keep the monetary economy going?
Now, take away the need for everything to be profitable. If we can technically create auto-cleaning toilets and there are no restrictions on doing that in principle, and there are no restrictions on how well we design them because there is no resource 'cost' in the monetary sense, which means we can design the best possible self-cleaning toilet that our ingenuity can muster, truly it would be a glory to behold!
So, to go back to the original point, the answer to the question "Who will clean the toilets" is really to re-frame the question to be "Why would anyone clean the toilets".
Our technical ability, though doubtlessly impressive is constantly being stymied by the demands of the monetary economy based on the idea of scarcity. Our technical ability is not a fraction of what it could be under an NLRBE.