There isn't, as far as I know. EPiServer Find, which is "event driven", doesn't even pick up permission changes.
I never used this, but In EPiServer 7/8, there is IContentSecurityRepository interface. The instance is available under ServiceLocator.
This interface is used by IContentSecurityDescriptorExtensions to save the access rights.
It expose public event ContentSecuritySaved.
ServiceLocator.Current.GetInstance<IContentSecurityRepository>().ContentSecuritySaved += .......
Maybe there is something similar in EPi 6 (like DataFactory could implement same event).
Is there a event that fires when access permissions for a page is changed? I have search high and low for days now and is starting to give up...