I believe that BHCC means BHC Completion, as already posted. BHCA
is already explained.
The relationship (for trunks with
blocking = 0%), is as follows:
BHCC = BHCA * ASR
where ASR means Attemping Size Ratio, or the probability for a
call to get a free channel and be
completed (0% Blocking factor).
ASR is to be measured after operations, but a rough estimate for it is between 0.65 and 0.8.