Actually had a nice surprise while walking home through a park last week, when, because the toilets were closed, two German sounding women were having a pee on the floor outside them.
They seemed a little shocked by my appearance, but I just smiled, stepped into the space between them and the wall and joined them in having a pee.
Totally unexpected but certainly a pleasant surprise!
Aside from that, I often go to music festivals and there are plenty of spots at those. Half the time if you're taking a pee somewhere to avoid the lines, they'll join you in the same area anyway. I don't complain.