What does the "BA/" stands for in this ATIS? LTBA ARR
  ATIS V
  0920Z EXP ILS DME APPCH 05 BA/ FOR RWY 05 TRL 110 AFTER VACATING RWY CONTACT 121.8 WIND RWY 05 340 DEG 07KT VRB BTN 310 AND 020 DEG VIS 9999 FEW/02000 FT BKN/03000 FT T 21 OP 15 QNH 1017 NOSIG
  END OF ATIS V
I think the BA/ references "Braking Action" in the ICAO D-ATIS sequence. Since the example report from LBTA (Istanbul Ataturk International Airport) does not suggest that a Braking Action value would be assigned (no rain, etc), it appears to be a placeholder for that information if it was provided.  

Below is an excerpt from Annex 11, to the publication - Convention on International Civil Aviation (Air Traffic Services), showing the sequencing (where it would normally appear in the D-ATIS report) of a Braking Action report (if provided/available).