I can't speak to the cost. It would have been a matter for the Canada Revenue Agency--additional costs.
As the minister has said, when a ways and means motion is tabled the Canada Revenue Agency will generally administer the law on the basis of that motion, which would have led to changes in the forms. If they came late in the year there certainly would have been costs if any reprinting of forms, etc., was required.
When the law was passed, the forms for that year or for the following year would have to be adjusted accordingly.