Really a question for @Olof and @Fredrik . Assume a Positive result is the Scanner determines luggage contains contraband; Negative is no contraband. If the Scanner determines luggage has no contraband and passes it through as safe, might the luggage actually contain contraband? That is, it should have been positive.
If a false negative is possible, then all luggage needs to process through Tier II and/or Tier III security. Thus, a Generic Scanner would be of no use. However, if the Generic Scanner never makes a false negative, then the Generic Scanner has value.