I'm trying to figure out how /etc/config/network is applied. I know that it is possible to run /etc/init.d/network reload and apply the changes. However, I can see that if I add, say, a new bridge or switch or interface, monitoring /var/log/messages indicates that these changes are applied as soon as the file is saved.

I tried to see if there is a process holding /etc/config/network open by running lsof /etc/config/network. Nothing shows up.

Does anyone know how this works?

Customizing UCI configs with CLI doesn't trigger service reload unless you call it over ubus API.
Service reload can be automatically issued by hotplug upon registering the service-related events.