Currently, we're receiving Site24x7 events for TROUBLE, DOWN and UP. Would be nice to include MAINTENANCE events since not all MAINTENANCE events involve code upgrades, some are infrastructure upgrades.
The reason we don't send notification for maintenance is because as IT Admins who actually manage the infrastructure (and monitor them), you know that the servers go into maintenance. Since its known, sending notification for that is usually considered as a noise. We however show the monitors under maintenance.
Typically end customers would want to know when a service can go into maintenance and the service might have some disruptions.
If that's what you want to have, I suggest you take a look into our Incident communication platform StatusIQ. Here you can create incidents with different status and customers can subscribe to it (you can control what you want to show to the end users).