This was permitted like a march, block party, or event.

But regardless NYC would be a better place if the spontaneous demonstrations we're used to seeing were more like Indian weddings.

Plaster and Lath walls, but there are absolutely still studs.

Best way to find them is to use a magnet, which will pick up the nails used to fasten the lath to the studs. Will usually stick on the wall in a straight line up and down. Once you've located stud, can screw into it like anything else.

Alternatives are to use toggles. I prefer snap toggles, but you'll need a 1/2 inch drill bit to drill the hole for them. If you're hanging something that's very heavy, I would definitely NOT rely exclusively on toggles on plaster/lath, as they're rated for drywall.

The other hack you can do on plaster and lath for something that isn't very heavy and is to take one of those gold picture hanging brackets and just swap the nail for a screw that you will screw down into plaster at an angle.