I may be mistaken—I don't have the budget before me—but I believe that a notice of ways and means motion concerning the change to the capital gains inclusion rate was attached to the budget submitted on April 16.
However, it is normal for the Canada Revenue Agency to begin administering a tax measure when a notice of ways and means motion is included in the budget. It facilitates administration of the tax system. Of course, there's always a chance that the measure may not be legislated into being and therefore not see the light of day. The government would then have to recalculate the amount of tax to be levied. However, it's common for many governments to request that the agency administer tax measures announced in a budget before they're adopted.