Yes, the extra matching contribution your employer puts into your group RRSP plan is considered employment income and so yes it would be included in the income reported on your T4.
However, you should also receive from your RRSP plan administrator a contribution receipt, and the amount on that receipt should include both your contributions and the $500. Consequently, you should be able to deduct that $500 from your income when you file your income tax return.
The net effect is that your employer's matching contribution goes into your RRSP without any present tax impact. You'll pay tax on the $500 later (or whatever amount it grows/shrinks to) when you eventually withdraw the money, presumably in retirement.
Note that your payroll income tax withholding amount may have already been adjusted (in your favor) to assume that you'll take the corresponding deduction for your payroll RRSP contributions. This means that if you don't get use your RRSP contribution receipt to claim the deduction on your income tax return, then you could end up with a balance owing.