I have the two larger boxes......curb pickup in good condition from about 6 years ago (even found some small wrenches and screwdrivers that fell behind the drawers). The guy had them hooked together in that configuration but he didn't toss the cart.
I dropped my wife (then girl friend) off at her house after a lunch date and there they were at the curb one block over with no other trash. I knocked on the door and asked if they were trash and the woman said take them. I had to park my car next to them and call for assistance as my car couldn't hold them.
Funny, back then I was too embarrassed to call and her tell her I was still in her neighborhood and waiting for help to pick up someone elses trash........now she is used to me picking up something from time to time.