In the interest of context, consider that within the last 8 months, the price of a barrel of West Texas Intermediate Crude has fallen by about 58% from a peak price of $107.95USD in June 2014. The price of Brent has fallen by approximately 60% from $115.19USD in the same month and the price of Western Canada heavy oil has fallen by about 50%, since a peak of $86.56USD in June 2014. The price fall is mainly a result of rapidly increasing world supply and in some cases falling demand. A relatively conservative short-term outlook (next 6 to 12 months) is for prices to remain below $60USD per barrel. Some have suggested a potential bottom price in the $20USD per barrel range.
The impact of the significant drop in oil prices will be negative on the Alberta, Saskatchewan and Newfoundland economies and their government revenues. It will also be negative on those First Nation economies and governments that are dependent on oil royalty revenues. The effect will be ameliorated somewhat if Canadian oil can more easily reach tidewater, since the current discounts are much harder to bear with low prices. As of December 2014, the price premium for Western Canada heavy oil shipped to tidewater was still about $19USD. This may actually lead to more urgency being attached to proposed pipelines (Energy East, Keystone, Kinder Morgan and Northern Gateway).
The fall in the value of the Canadian dollar relative to the US dollar will make many Canadian exports more competitive on the world market. It could boost exports and investment into industries in BC, Ontario and Quebec. It could also lead to increased investment, employment and government revenues in First Nations that export non-oil resources and goods.
The mining industry should do relatively well as a result of the fall in the value of the Canadian dollar. The exchange rate is one of the most significant determinants of the profitability of investments into mining. If the price of a commodity such as gold is on the rise, then significant investment interest should be expected.
However since, most short-term projections are for oil to remain below $60 a barrel, the overall impact on the Canadian economy and federal revenues at this price will be negative in the short-term.
Medium-term projections and impacts are difficult to determine because there are two factors that could keep prices lower and two factors that could increase prices. Prices could stay low if OPEC and other oil revenue dependent governments maintain current production levels. Conversely, prices could rise if there is supply and political uncertainty in significant oil producing countries (Russia, Nigeria, Venezuela, Yemen, Iran, Saudi Arabia) or a sustained economic recovery.
It is no coincidence that the federal government postponed the release of its budget until it better understands the impact of the oil price decline on its projected revenues and expenditures.
 Shenk. M. (2015). U.S. Cuts Oil Output Outlook as Price Drop Slows Drilling. http://www.bloomberg.com/news/2015-01-13/u-s-cuts-2015-oil-output-forecast-as-lower-prices-slow-drilling.html.
 Kaletsky, A. (2014). The reason oil could drop as low as $20 per barrel. http://blogs.reuters.com/anatole-kaletsky/2014/12/19/the-reason-oil-could-drop-as-low-as-20-per-barrel/.
 This is represented by the difference in the monthly average Brent Crude Oil price and the Western Canadian Select Crude Oil price for December 2014.