I know GM dealerships had/have fleet managers, mostly to handle trucks for construction, gas, power companies, etc. Holdback is a percent of the MSRP (sticker price) of the car that the dealer receives from the manufacturer after the car/truck has been sold. It's always kept by the dealer to help pay for overhead, advertising, etc. I'm thinking maybe if there was a fleet purchase, they actually discounted the cars the additional holdback money. Didn't GM sell a bunch of turbo regals to the FBI? If so, those would have probably fallen under that same program.