What electrical anomaly can cause RCBOs to trip in apartments in several buildings at the same time?
Some RCDs open their contacts when the supplying net shuts off and do not automatically reconnect when the power returns. A brief black-out (say, some 10&nbsp;ms) may be enough.

Your substation may have experienced such a black-out.

To be sure, you could try to find a data sheet of your particular model or do a test if you are able to safely turn off the net supplying your RCD.

If refrigerators or alarm clocks are connected to such RCDs, such a behavior would be a major annoyance. If machines, stoves or tools are connected, they may remain switched on while unpowered and you may even need this feature to avoid unintentional turn-on once the power to your home returns.