I believe it. I'd rather not roll the dice on getting a neighbor that will do it right though.

presumably the same rules that you trust for neighbors to work on their own plumbing/landscaping and preventing runoff into your yard, for example, would apply here.

I think the issue is that with slightly bigger lots and/or city services meant to alleviate these problems (sewage lines), much of what might be problems is smoothed over. Often there are laws about setbacks from property edges for dwellings, which may or may not apply to a structure which is not meant to be a dwelling. By skirting the rules or using a loophole, people may in some instances find why those rules were put in place in urban areas (i.e. where people live closely together).

I am not sure I actually want a lot of details but I am too curious not to ask.

> with the right separation of pee/poop

How does one do this logistically? Does this mean a compost system where you have two distinct toilets/containers for each of those bodily functions?

The ones I've seen have a slanted pedal-powered conveyor belt inside the bowl. Liquids run down to the front, and then you pump the pedal a few times to crank the solids to the back.