With the recent Laravel 5.8 release, it is now a lot easier to listen for Eloquent Pivot events. There are a lot of ways on how you can listen to Pivot Events and here's one way using Model Observers.
Also, if you did not know, you can define a model for your pivot table using the following command
php artisan make:model PivotModelName --pivot. An Eloquent model will be generated which you can use to define relationships back to owning Models.
ProTip: This is really useful especially if you have 3 or more owning Models in a Pivot table.