Generate hotplug.d events for usb on boot


I want to generate uci default network configuration if i plug in a usb LTE modem.
(Want to get the AT-Command tty interface and some other parameters)
This is not working if i boot. If I unplug and plug in the modem again then it is working.
Do I miss something?

By the way where are the hotplug events generated for usb devices is it the procd?
If so can some one show me the right place in the sources?