they ferried it empty home to FRA - so, if it is considered airworthy why not loaded then
There is a difference between "airworthy" and "flyable." An airworthy aircraft is one with no defects noted outside those allowed by the MEL/DDG/CDL manuals. Since I doubt Airbus included "damage to structure caused by jetbridge" to these manuals, the aircraft is not airworthy and not fit for commercial service. But that doesn't mean it won't fly. A "ferry permit" is an authorization to fly a non-airworthy aircraft, normally with some limitations. Almost always one limitation will be only required crew may be aboard. Doing two engine ferries on 727s, the departure runway had to be dry and it had to VFR at the departure and destination. Either the local CAA will issue the ferry permit or if the operator has a decent engineering staff they will authorize the operator to issue them inhouse. I always thought the mechanic that signed the log book, "I have inspected this aircraft and found it suitable for flight from ABC to XYZ" was really hanging everything out.