I find these situations very weird. We know the JWs have a major internal problem with "inappropriate" sexual goings-on (to put it mildly), but in the congregations I've been in (admittedly not many), situations like this just wouldn't have happened (at least not openly as reported here).
Maybe it's because I'm in an English inner city where elders tend to be much more wary and on the look-out for anything that hints of "immorality", but any kind of arrangement like the one described would've been stamped on very quickly. In my experience, it's difficult enough to make a regular ministry arrangement with a single "sister" at any time without people making comments about whether one of you is "interested" in the other, and even just a brother sitting next to a sister at the meetings a few times would get attention! Even in social groups, "younger ones" tend to be "encouraged" not to gather together too much without adults and/or family members being involved in the groupings.
It all makes it rather stifling and dull for grown adults and single ones who genuinely want to mingle with the opposite sex without being over-policed, but it does at least mean the elders are not allowing the kind of lax contact that I frequently read of on here, which has led to so many shocking incidents.