Good griefs. That is a new one for me. I would not expect to see couches & refrigerators dumped into manholes anywhere.
Some places have combined sewers where storm water drains into the same underground channes and pipes as sanitary sewage; it would be hard to dump couches and refrigerators there. But that's usually seen in cities with very old infrastructure: combined sewers don't make sense when you have sewage treatment plants. During a storm you have a lot more flow, and you'll exceed the capacity of your treatment plant and have to let untreated water through. Even in separate sewers, you have higher flow in the rainy season; utility sewer pipes aren't usually sealed at connections, so if there's a lot of ground water, it leaks into the pipes and flows through; the change in volume during a storm is usually not that fast, but flow rates during the rainy season will be significantly higher than the dry season.
Sounds like Tijuana has separate sewers, but lots of unauthorized connections from indoor plumbing to the storm sewers.
In peninsula there are separate storm drains in the streets. Better in theory! But they don’t permit a direct connection from your French drain’s sump pump into the storm system. So some people pump into their household sewer instead.