Well, as expected, the collective bargaining agreement between AA and APFA has all of our answers. Here are relevant excerpts:
From Appendix ZZ, Letter I:
On domestic flights and on international flights of less than five (5) hours of scheduled flying time, if a passenger is either assigned or requests to move to a designated crew rest seat, the passenger's request will be accommodated.
On domestic flights and on international flights of five (5) hours or more but less than eight (8) hours scheduled flying time, if a passenger is either assigned or requests to move to a designated crew rest seat, prior to takeoff, the passenger's request will be accommodated. On such flights, after takeoff, a passenger who requests to move to a designated crew rest seat will be accommodated at the discretion of the Purser or Lead Flight Attendant.
On international flights of eight (8) hours or greater scheduled flying time, designated crew rest seat/bunks as set forth in Appendix I., Article 30.L. will be provided solely for the use of Flight Attendants.
From Appendix ZZ, Letter II:
The APFA agrees that the Company is not restricted from assigning any available seat according to its established Customer Service policies and procedures (including those established pursuant to paragraph 1. above). The APFA recognizes that a passenger should not be denied accommodation for a seat, nor should a Flight Attendant deny a request by a passenger to move into an open seat in order to retain a seat for Flight Attendant personal use for in-flight rest, except that, after takeoff, a passenger who requests to move to a designated crew rest seat will be accommodated at the discretion of the Purser or Lead Flight Attendant. Furthermore, the APFA agrees that Flight Attendants should not request Customer Service personnel to withhold seating from passengers beyond that which is provided by the Company's policies and procedures.
From Appendix ZZ, Letter VI:
In the event one (1) or more Bunks/Crew Rest Seats become unavailable for use due to a significant malfunction, the Company will provide substitute Crew Rest Seats as follows:
For flights eight (8) hours or more scheduled flying time but not exceeding twelve (12) hours scheduled flying time, one (1) regular Main Cabin passenger seat will be provided on a one-for-one basis for each Crew Rest Seat which is unusable.
For flights over twelve (12) hours scheduled flying time on 777 aircraft configured with bunks, one (1) regular Business Class passenger seat will be provided on a one-for-one basis for each Bunk which is unusable, if a Business Class passenger seat is available. Should a Business Class passenger seat be unavailable, a Main Cabin passenger seat will be made available.
For the purposes of this letter, “significant malfunction” will mean a lack of functionality. Examples of significant malfunctions will include: the crew rest seat has no recline or the seat cushion is missing or there is no oxygen access to a bunk/seat. Examples which do not constitute a significant malfunction include: a lack of a reading light or missing curtain or an inoperative footrest.
From Appendix ZZ, Letter XI:
During the interim period while the 767-300 aircraft is being modified to install the new crew rest seat accommodations, the Company will designate two (2) Main Cabin seats as crew rest seats in addition to the existing crew rest double.