Well, that prevents you from owing money at the end of the year but you end up paying the same amount of tax either way - you're just tweaking when the tax actually gets paid.
Given that Federal tax rates are:
15% on the first $38,832 of taxable income, +
22% on the next $38,832 of taxable income (on the portion of taxable income between $38,832 and $77,664), +
26% on the next $48,600 of taxable income (on the portion of taxable income between $77,664 and $126,264)
What I'm wondering is if there is a way for the pay people to do something like go back and reissue T4s with the applicable increases for each year, and then recalculate income tax for each year - which would probably result in three years where the income would remain below $77,664 (which is the limit of the 22% rate scale). That would certainly mean paying less taxes than having the lump sum reported in 2009, which would push income into the $77,664 to $126,264 tax bracket and have the bulk of the back pay taxed at 26% (for Federal tax, anyways).
What I don't know is: Can you do that, or something that achieves the same result?