I know that there were AFAIR 13 EWI A in the combined BLS/SEZ/BN fleet. This was the model by Lima for the late 70s/early 80s:
309513: 50 63 18-33 806-2
I have books which provide road numbers for coaches for SBB rolling stock. I do not have the same information for BLS coaches.
I also have information in books for SOB and BT but never came across similar for the BLS Group.
Markus likely has more information and it would be cool if he could provide a source (book) for same.