Hello,
The PPPoE client in the subscriber module should perform retries in the event of a PPPoE session disconnect. How quickly a session disconnect is detected and a retry is performed will depend on your Keep Alive timer ( http://community.cambiumnetworks.com/t5/ePMP-Networking/ePMP-PPPoE-Configuration-and-Troubleshooting-Considerations/m-p/49604#U49604 ).
Regards