ACR FLC ATTEMPTS WRONG RWY TKOF AT MIA.

Narrative

THE PREFLT DUTIES WERE BUSY AS WITH A FERRY FLT WE HAVE SOME ADDITIONAL ITEMS TO CHK AND SET UP. AFTER ALL CHKLISTS; PUSHBACK; AND NORMAL ENG START; WE RECEIVED TAXI CLRNC TO RWY 9L. RWY 9L WAS IN THE FMC. APCHING THE RWY; THE TWR SAID WHAT WE BELIEVED TO BE 'CHANGE DEP FREQ TO 'GARBLED' TAXI INTO POS AND HOLD.' I READ BACK 'RWY 9L POS AND HOLD; WHAT WAS THE DEP FREQ?' TWR READ BACK THE SAME FREQ WE HAD FROM OUR CLRNC. IN LOOKING BACK AT WHAT HAPPENED; THE TWR MUST HAVE SAID 'CHANGE THE RWY TO RWY 12; TAXI INTO POS AND HOLD.' ALTHOUGH I READ BACK 'RWY 9L TAXI INTO POS AND HOLD;' THE CTLR MUST HAVE BEEN CONCENTRATING ON THE QUESTION OF WHAT WAS THE 'NEW' DEP FREQ. CONTRIBUTING FACTORS MAY INCLUDE A TREMENDOUS AMOUNT OF CONSTRUCTION CLOSING NUMEROUS TXWYS. ADDITIONALLY; OUR TCASII; WHEN TURNED ON GOING INTO POS; WAS NOT WORKING; SO WHEN WE LOOKED OUT AT THE FINAL APCH; IT WAS DIFFICULT TO DETERMINE WHETHER THE ACFT ON FINAL WAS 2 MI OUT OR 5 MI AT NIGHT. SUPPLEMENTAL INFO FROM ACN 464160: AT THIS TIME WE STARTED TO ENTER RWY 9L FOR TKOF. AT THIS POINT; TWR TOLD US TO VACATE RWY 9L THAT WE WERE TOLD INSTEAD TO TAKE OFF ON RWY 12. WE BOTH THOUGHT WE HEARD A READBACK OVER TWR FREQ CLRED FOR TKOF RWY 9L. WE THEN QUERIED TWR AND HE STATED HE CHANGED TKOF RWY TO RWY 12 AT END OF HIS LAST XMISSION.