The following information from CRA states that your premiums are not deductible if the trust pays them. If they pay them, your employer does not include them as a taxable benefit to you and you cannot claim a medical expense deduction.
Contributions to a private health services plan1.35 Contributions made by a health and welfare trust to a private health services plan are specifically excluded from employment income by subparagraph 6(1)(a)(i). The benefits received by an employee under a private health services plan are also not taxable. Private health services plan premiums, contributions, or other consideration paid for by the trust cannot be claimed by an employee under paragraph 118.2(2)(q) as eligible medical expenses.
If you are paying these premiums out of your own pocket, you can claim them as a medical expense.