This has happened regularly both in BC and Canada federally. The "unexpected" surplus always is credited to "a stronger-than-expected economy".
What is actually happening is Ottawa is collecting far more money than it has programmed spending for. At the same time it fends off legitimate demands for earlier cuts to be restored or essential programs such as dependable regular funding of urban transit systems or low cost social housing - or even essential health care spending to cut waiting lists and the need to keep sending Canadians south of the border for essential (but much more expensive) care there. Not to mention the poor Canadian troops paid a pittance and put in harm's way without decent equipment.
And the response will not be more spending on these essentials. But will go to pay down the debt - yippee! Or maybe a few more strategic tax cuts to benefit the well off Tory voters.