i have not yet stayed myself at that rate, but when you read the rate description, it does not say you need proof.. i feel fine to use it..

-No points/miles awarded
1 night minimum stay required.
Special rate offer is available to all employees, affiliates, partners, franchisees, friends and family of the entire Carlson organization including, Carlson Marketing, Carlson Wagonlit Travel, Carlson Restaurants Worldwide and Carlson Hotels Worldwide.-