Gerrit has a feature where events are announced to ssh connections

https://gerrit-documentation.storage.googleapis.com/Documentation/2.9/cmd-stream-events.html

Other services can use this feature to respond to these events like push notifications. So a CI build system can use these events to trigger a build when a change set is created/updated, or when a change set is merged, or when something is pushed directly to a branch bypassing review, etc. I believe this is how the Jenkins Gerrit Trigger plugin works.

https://wiki.jenkins-ci.org/display/JENKINS/Gerrit+Trigger#GerritTrigger-TriggerConfiguration

The Gerrit plugin would need an update so that any time a configuration is saved with a Gerrit repo, an overall mapping of Gerrit projects to configurations is maintained. When an event is received, QuickBuild looks up the mapping and triggers every configuration using that project and branch.

This could potentially be handled in the reverse direction by configuring the Gerrit server with a hook script to make a REST call to the QuickBuild server, but QuickBuild would still need the maintain the mapping of projects -> configurations.