I have actually been looking into this myself recently, and the short answer is yes... if there is a tax benefit associated with the expense (ie medical expenses, child's activity amount, child's art amount) it should be considered with the benefit. My interpretation is that the tax benefit is taken of the top and the rest is shared. Also (I actually asked this in this same forum a few days ago) Benefits paid from CCRA for the child is included as income for apportioning the s. 7 expenses.
Here are the relevant sections from the Guidelines (if I'm understanding your question correctly).
From:
Family Law Act - O. Reg. 391/97
Subsidies, tax deductions, etc.
(3) Subject to subsection (4), in determining the amount of an expense referred to in subsection (1), the court must take into account any subsidies, benefits or income tax deductions or credits relating to the expense, and any eligibility to claim a subsidy, benefit or income tax deduction or credit relating to the expense. O. Reg. 159/07, s. 2.
And from:
Family Law Act - O. Reg. 391/97
Special or extraordinary expenses
3.1 To calculate income for the purpose of determining an amount under section 7 of this Regulation, deduct the support, not including child support, paid to the other parent or spouse and, as applicable, make the following adjustment in respect of universal child care benefits:
(a) deduct benefits that are included to determine the parent or spouse’s total income in the T1 General form issued by the Canada Revenue Agency and that are for a child for whom special or extraordinary expenses are not being requested; or
(b) include benefits that are not included to determine the parent or spouse’s total income in the T1 General form issued by the Canada Revenue Agency and that are received by the parent or spouse for a child for whom special or extraordinary expenses are being requested.