In your quest for the best "pissotières" while visiting France, you are forgetting one of the best thing that McDo has to offer... Leurs pommes frites...
Non, non and non ... Please don't call those delicious potatoes "French Fries" there are no such things as "French Fries", only in the mind of those that do not know their potatoes from "horse apples"...
Frites are a Belgian things, and therefore when the Washington morons changed the name "French Fries" to "Liberty Fries" a few years ago, they only made "trous du cul" out of themselves and insulted Belgium, not France...
In France long ago, one could stop by a street vendor to buy a delicious "Cornet de frites"... Back then, they tasted a whole lot better than what is being served now in the French restaurants or anywhere else...
Then came McDo... Oh mon Dieu, I could not believe it, their frites tasted good, just like the ones I used to buy from the street merchants in Rouen before the "health Fanatics" made McDo alter their recipe...
Back to the best place for one to answer the call of nature...
Moi, I suffer from "pissotièrephobia" when I am in France...
I have this fear of using those funny cubicles in the streets of Paris, fear that the "Wash Cycle" will start before "Mission accomplished" giving a new meaning to the expression "Caught with your pants down"...
Of course, one can always go to a café for a drink and to use their facilities while performing a delicate "balancing" act at some old places, but why not just go to a McDo for an order of "Fries" if need be and use their "High Tech" WC?
Or, is there such things as "BP" stations in France???
Mike