The following is now available on the CBSA Web site:
Memorandum D13-3-12, Treatment of Assists in the Determination of the Value for Duty
http://www.cbsa-asfc.gc.ca/publications/dm-md/d13/d13-3-12-eng.html
In Brief
Memorandum D13-4-8, Assists (Customs Act, Section 48), will be cancelled. Information from the former D13-4-8 is now included in this memorandum.