CRJ700 FLT CREW HAS ANOTHER ACFT CLRED FOR THE SAME APCH AT ATL.

Narrative

ATL WAS RUNNING SIMULTANEOUS APCHS IN VFR CONDITIONS TO THE S RWYS AT ATL; RWYS 28 (NEW) AND 27L. ENTERING THE ATL APCH AIRSPACE; THIS CREW WAS TOLD TO EXPECT TO LAND ON RWY 27L. THE CREW CHANGED THE FMS APCH FROM RWY 28 TO THE ANTICIPATED RWY 27L RWY WITH THE ASSOCIATED LOC FREQ 108.5. FO WAS FLYING. WE WERE SWITCHED TO THE FIRST CTLR AT 118.35 WITH NO WORD OF CHANGE OF A DIFFERENT APCH TO RWY 28. THUS; WE REMAINED SET UP FOR RWY 27L. CLRED TO DSND TO 4500 FT MSL AND CLRED TO TURN BASE. SUBSEQUENTLY CLRED BY FINAL TO JOIN THE LOC OUTSIDE THE FAF -- DEPOT. THERE IS A GREAT DEAL OF RADIO TFC BTWN FINAL AND AN ACFT IN FRONT OF US. THE ACFT IS ON THE ILS APCH FOR RWY 27L WHEN INFORMED TO CHANGE TO RWY 28. THE OTHER ACFT ASKS FOR AND RECEIVES THE ILS FREQ FOR RWY 27; 111.75. DURING THE ABOVE SCENARIO; I NOTICED A TCAS SYMBOL DIRECTLY ABOVE MY ACFT +1000 FT. WE WERE BOTH ON THE LOC FOR RWY 27L WITH ABOUT 1800 FT SEPARATION AND DSNDING. I CANNOT REMEMBER ONE ASSIGNED ALT. I 'BELIEVE' I ASKED THE FINAL CTLR ABOUT THE ACFT ABOVE AND WAS TOLD TO DSND AND TURN IMMEDIATELY OFF THE LOC. WE TURNED AND DSNDED TO 2800 FT MSL. FINAL CLRED US TO JOIN LOC FOR RWY 28 AND GAVE US FREQ 111.75. SWITCHED TO TWR AND CLRED TO LAND ON RWY 28. ON SHORT FINAL AND WANTING FURTHER VERIFICATION; I ASKED FOR LNDG CLRNC; TWR CLRED US TO LAND ON RWY 27L(?) TWR QUICKLY REALIZED THAT WAS NOT CORRECT AND VERIFIED RWY 28 LNDG CLRNC.