I have used both core and foil CIC boards and it is more challenging than non
metal boards.  The rework was easier than the original profiling.  That is
good.  The need for touch up after reflow was common place.  I never did
BGAs, but the need for heat in a BGA and the need for heat in CIC combined
with elongation of duration lends this CIC/BGA configuration as a predictable
need for touch up (can't touch up under a BGA easily).  I might advise to
attach the BGAs after initial solder float. It is not very economical, but
then again neither is CIC.

I have had success with CIC and Thermount.  Thermount has all but killed CIC
although there are moisture issues with Thermount.  I say this relative to
the ongoing existence of CIC.  The rumor mill had it that CIC was going the
way of Howefill... discontinued.

Coretec Brad
781 858 0783