Hi Lacyr,
The group enrollment does not need you to have all the individuals participate with Medicare as a mandate. You may have individuals who wish not to participate with the payer too. It's just those individuals won't get paid if they treat medicare patients. In your case, the PT is already Par with Medicare. So, as Michele stated, a CMS-855B for the group enrollment, a CMS-460 for the participating provider agreement, a CMS-588 for the EFT agreement and a CMS-855R for reassigning the PTs benefits to the group would suffice.
Just so you know, Medicare would do a site visit for audit before approving the group application. Therefore, make sure you list all the service locations on the application form especially the one where the PT would practice. Hope this helps. Good luck.