Officemax's official corporate policy changed and they do NOT take competitor's coupons anymore. They do not mention anything about accepting competitor's coupons in their pricematch section or 115% guarantee section online either.
This doesn't mean you don't have clerks or even managers who are either ignorant of this change, just don't care, or if a manager, even willing to override it and honor a competitor's coupon. It does mean it's now one big YMMV and no one should expect or bank on the ability to use an OD, staples, etc coupon at OM anymore since OM changed their official policy. It's also a big YMMV with phone in orders as well, though much less likely to work on average since they are more informed of official corp policy than every single OM employee scattered across the US.