In general since we are a net oil exporter, in the short run there will definitely be a negative impact on revenue through lower corporate taxes.
The complexity of that issue is lower oil prices will benefit other sectors of the economy and also consumers because consumers will have more real income available to spend on other things.
So over time typically you get that negative impact on the revenues in the first year, and then the other sectors of the economy will adjust to lower energy prices and lower costs so some of that negative impact will disappear over time.
In the end the net impact on government revenue in Canada may be very small.