another twist to the employee only thing

I am at a site for where I work where we have "casual" (PT on call employees who reside all over the country) who never have stepped foot in any of our offices and are called to assignments that are 100% travel; what I didn't realize until today was that we do not issue them ANY form of identication (badge, card, biz card etc) yet they are eligible for all of our corporate rates; how they prove it I'm not sure but this just goes to show that not all employees have ID