Are employer funded medical expense reimbursements taxable?

We have a high deductible group health plan (BCBS).  Employer also pays for out of pocket medical reimbursements (deductibles).  Employee does not pay into a fund for these reimbursements.  For the first two years of a three year contract, these reimbursements were paid out at the full amount of the expense.  This year, a new office assistant took taxes out of the reimbursement.  Did something in the tax laws change or did she do this incorrectly?