That's a great question about a common piece of city furniture! The answer is generally yes, most ashtray tops on public trash cans are designed to be removed for cleaning. Municipalities install them specifically to reduce cigarette litter on sidewalks, and regular maintenance is crucial for them to function properly.
Typically, the metal or plastic ashtray cup sits in a receptacle on top of the bin. Maintenance crews usually lift them out by hand—they are not screwed or permanently fastened. This allows for easy emptying of the ash and butts, and for the unit to be rinsed or washed. Some modern designs even have a simple latch or twist-lock mechanism for secure but removable placement.
If you're a resident looking to help, it's best not to attempt removal yourself. For safety and hygiene reasons, cleaning is handled by authorized city sanitation or public works departments on a scheduled basis. You can, however, help by properly extinguishing cigarettes in the provided receptacles and reporting full or damaged units to your local council's waste management line. Keeping these ashtrays functional is a simple way to maintain cleaner streets for everyone.