There may be a way to create a custom wrapper service that simply makes a post to the ExtensionPackageUploader REST service and passes the extension as a binary parameter. You could then use an event from this service to trigger the add entry service. The URL to make the post to would looks something like this: http://<server>/Thingworx/ExtensionPackageUploader.
I am not sure if any event is fired when there is a successful extension import.
You can try to use timer event and check at some interval regularly for GetExtensionPackageList service of PlatformSubsystem. So, if there is any change in count; we call call our custom service to update the DataTable.
Could you please explain how are you using the DataTable in Utilities? A better way would be to use GetExtensionPackageList service of PlatformSubsystem directly and show the current data.
We can create a custom Service with GetExtensionPackageList service wrapped and show the Data according to our requirement.