Cepro.com has an article  that gives some good examples of integrating lighting control with security:

- Programmable dimmers and switches to go 'all on' when the security system is tripped

- Flashing exterior lights when the security system is tripped

- Timed away lights can be used to make it look like someone is home when the security system is in 'away' mode

- Pathway lighting activated by motion sensors when the security system is set to 'sleep' or perimeter mode so you can get to the bathroom or fridge safely

- Welcome mode can be programmed to turn on certain lights or activate scenes when the security system is unarmed

- Escape routes can be illuminated in the event of a fire alarm

There are other integrations as well, but this gives you a good idea of the benefits of tying the two subsystems together.