I was actually thinking about this yesterday. I had stopped in a fast-food joint on my way home from an appointment. There's a trend where in small restaurants and other businesses the restroom with a urinal and stalls has been replaced with an ADA-compliant handicapped accessible restroom with a single toilet and - yes! - a lock on the door.
The first time I noticed one of these I thought to myself, "Wow, this is big enough to have a party in here!"
This particular place had the door visible to the food service counter, so it would have really worked to stay too long inside nor -- my fantasy -- to get one or more guys in there with me.
Anyhow, I had someplace to be so I didn't stay. There was another similar restroom I'd been at last summer here in Houston at a nursery (garden center) which was basically deserted. It had old cinderblock walls and a dirty sleazy neglected air about it. You could just picture acting out the J/O scene in the toilet from Joe Gage's "LA Tool & Die" in there. Only thing missing was a gloryhole.
Bottom line, if I had the time and opportunity I'd want to do it. I should get back into that scene and post some reviews in the Sex Listings about what happens.