How would a pension get divided, or the decision made?

First, under Ontario law there is a conceptual distinction between your wife’s entitlement to support (whether child or spousal) and the manner in which your assets are divided and shared.  A pension is considered to be assets, which are added up as part of determining your and your wife’s Net Family Property (NFP).  So the fact that you are paying support to your wife does not directly impact the treatment of her pension, or allow for any flexibility or decision-making around it.

Your wife’s pension is automatically included in the NFP equalization process, which involves each of you tallying your respective assets, and then calculating the difference between each of your NFPs.  The court will then order an adjustment so that each of you has the same net worth.

Again, your wife’s pension will be included in this straightforward calculation, although the court does have several methods it may choose for attributing value to her pension for these purposes.