Ask for invite any allied squadron flying this event, and dont forget to register for medals-avards
U can try to do that earlier on BB or be 30 minutes before frame start, swich to allies and ask on main country channel CO.
Possibly chn 145 will be for walkons, ask there too.
If that not works, ask any squad member for permission to join his squadron. He redirect your request to his own squad lider.
ramzey