Thank you for posting to the PayPal Sandbox Community.
You can use the same IPN listener for more than one Sandbox PayPal Account. You can put the same Listener URL or use notify_url and pass in your listener url in your code.
You cannot have more than one IPN listener URL set in the PayPal Account, however, you can also use the notify_url variable in your code to set your IPN listener URL. This allows you to have more than one listener affiliated with one PayPal Account.