That's a great question, and one that city planners and public works departments think about constantly. From my experience observing cities, the short answer is: it depends heavily on the specific design, material, and location of the trash can.
Modern urban trash cans are often engineered specifically to withstand vandalism better than older models. You'll see a lot of heavy-gauge stainless steel or coated steel cans now. The smooth, hard surfaces aren't just for looks; they make it much harder to stick adhesives to, and graffiti can often be power-washed off relatively easily. Designs are becoming more seamless, with fewer protruding parts that can be snapped or pried off. Many are now bolted directly into concrete with specialized security fasteners to prevent them from being easily tipped over or stolen.
That said, no trash can is truly "vandal-proof." Determined individuals can still find ways to damage them. You might see dents from kicks or strikes, stubborn spray paint in textured areas, or occasionally a broken lid mechanism. The bins in high-traffic, well-lit areas like main squares tend to hold up remarkably well. It's the ones tucked away in quieter parks or subway stations that often show more wear and tear.
So, while they're not indestructible, the current generation of public trash cans is significantly more resilient than what we had 20 or 30 years ago. The focus is on making vandalism difficult, time-consuming, and ultimately less satisfying, which does seem to help. The best designs balance durability, maintenance cost, and of course, actual utility for collecting litter.