wasn't the 2015 budget based on growth averaging around 2.6% a year leading to the balance forecast for 2017/2018? Is growth of 2.5% - 3% not sort of inline with that projection rather than "big growth"?Almost certainly, a carbon tax was part of the funding plan and now it's necessary for Canada to meet it's promises.
That said, Wynne is getting a huge gift with the collapse of oil. GDP growth for Ontario in the second half of 2015 has skyrocketed and 2016/2017 are looking like they'll be big growth years (2.5% to 3%).
That adds about $4B/year to the revenue pot for the 2017/2018 budget. Makes closing the deficit gap much easier and greatly increases Ontario's borrowing limit for capital projects. The downside is tenders will probably go up (parts/components sourced from outside Canada).