Are the HBZ's and HCA's both scarce?
Hi "russ." Welcome to CPMF. The short answer is "no" as neither prefix is scarce. As of today (06/25/19) the SNDB reports that:
HBZ - 2,584 note entered & HCA - has 2,627 notes entered by various members of the CPMF. Such high numbers suggest they're very common. Since you have access to this forum- you will also have access to the "Serial Number DB" icon in between "Calendar" and "Logout" icons and you can check these figures for yourself.
As far as I can tell, from the SNDB data, there doesn't appear to be any scarce prefixes for the $5 polymer. Below are the figures for the following Macklem-Poloz HCG/HCM prefixes. Incidentally, the "HCG" thread you posted to was created because it appeared that the prefix was delayed in terms of its release. To give some perspective, I have also copied down the M/P HCM change-over entry:
HCG -763
HCM -854
486 of the Wilkins/Poloz HCM prefixes have been entered. Since it was released well after the first HCM I would not consider this change-over scarce either. The $50 Macklem/Carney GHD has 52 entries and it has been out for 7 years. Since not as many members enter $50 notes I would just consider this prefix is a "tough" one to find (or uncommon) but not scarce.
For M/C $10 FTH (13 entered) and the M/C $20 BSW (14) [or the M/C $50 AMK & $100 EHZ] it's a different story. These prefixes have been out for around 7-8 years & their low numbers would suggest that few were released into circulation.