This is taken from the thread on the commemorative $20 banknote:
The BoC is data mining using the currency's serial numbers, and are using the $20 commemorative polymer note as a pilot for this new process.
If anyone is interested more on this topic and some of the possibilities with respect to tracking of banknotes from a technological perspective may find this paper interesting:
"Banknote tracking as a toll for counter terrorism financing"
http://hadmernok.hu/132_04_padanyij_vgy.pdf
