My current (and past) company require AmEx Corporate for business expenses, but also do not allow MR, even if we pay the fee. From reading other threads, it seems this is because AmEx charges the company a fee (beyond the $75) to manage all of those points. Nice, huh?
If anyone knows of a way for me to earn points for my corporate AmEx spending (which is not huge), PM me. (and no, I can't move the charges to another card, they require us to use the AmEx.)