I think we are confusing localities with species.
Boa constrictor imperator is the species and CA or colombian is the locality. I'm pretty sure both CA and colombian are BCI (colombian can also be BCC). Though I think there is still a size difference alot has to do with feeding.

An average Colombian BCI female will be 6-8' depending on feeding and a male 4-6'. My girl is almost 3 years old and probably won't get much bigger then 6'.

IMO feeding has the biggest impact on size.

Here's a great website http://www.riobravoreptiles.com/