No.  Here is CRA’s view on why such a payment cannot be receipted.

Policy Commentary
Release Date
June 23, 1993
Reference Number
CPC – 008
Gift – Whether the payment to a registered charity instead of paying union dues is voluntary and therefore considered a gift
To clarify the Directorate’s policy regarding payments to a registered charity.
1. A payment to a registered charity in lieu of paying union dues is not considered a gift. For example, a company employee, for religious reasons, objects to paying union dues. The collective agreement under which the employee works contains a provision allowing the employee to pay an equivalent amount to a registered charity in place of union dues. There is an expression of free will on the part of the payer only to the extent that the payment is directed to a registered charity rather than the union.
2. The payment of a sum to the union or to a charity in the context of adhering to a collective agreement can be seen as making a payment for consideration; that is, in return for paying the amount, the employee gets a job. The presence of a substantial consideration invalidates the payment as a gift.
• Income Tax Act, R.S.C. 1985 (5th supp.) c. 1, para. 8(1)(i).