There is so much mystery surrounding currency distribution that is indeed fascinating.
Although there is evidence that there is inventory control of banknote distribution (see article by BoC on their website) the level to which there is control does not appear to be publicly known. It is known for instance that the BoC along with the Regional Distribution Centres is able to put more notes into circulation and pull notes out of circulation. It is also know that the BoC knows exactly the level of inventory there is at the BoC and each of the Regional Distribution Centres.
It is also known that the BoC is able to carry out fitness tests of banknotes and remove them completely from circulation or put them back into circulation.
One can surmise from the GOG test banknote case that the BoC had at that time some mechanism to capture very specific banknotes with very specific prefix and a narrow range of serial numbers as they came back into their system from circulation. Otherwise how would they even know how these notes were doing in circulation. Can you imagine someone going through all the notes manually at BoC just to find the GOG? There has to be a better way for BoC to know about it than a manual process.
If the BoC was able to do this work more than a decade ago is it not possible that things have just improved.
If you search hard enough and put two and two to gather I am sure you will find evidence that there is equipment that can identify the prefix and serial number of a banknote at very high speeds. The prefix and serial numbers are machine readable as printed.
Something tells me that the BoC knows exactly (prefix and serial numbers) which notes have been taken out of circulation at the end of their life.
Finally if these things were absolutely random why do we see a whole slew of HP? notes but no HAE+ notes. Okay you may aruge that maybe only limited HAE+ were printed but then can you explain to me EKZ. These notes are printed (I am guessing they were among the first to be printed because everywhere in the BoC videos they are featured)
This would be considered enough of an anecdotal evidence in terms of the research world to begin to believe that there is some form of control on currency maybe note at the serial number level but at least at the prefix level.
I am new to this hobby but I think the numismatic industry as a collective can certainly play a greater role in trying to get information from the BoC. While there are certainly matters of security many of the things that the numismatic industry wants are simple non-security type of facts.
I have heard from many that the BoC is not willing to entertain any questions. But I am a firm believer that if you approach it as an group of well meaning people then there is bound to be something that comes out of it.
The BEP (US) has videos and other information about their processes. Similarly there is information about the Danish banknotes and to some extent even the Euros. Even the Australian bank has some information their website for the numismatic world and I believe they even sell notes directly to collectors.
For the same type of information on Canadian banknotes we have to guess. Just beats me. But then what do you expect from a newbie