It depends entirely on the toll provider. Some of them definitely have Hertz registered for the photo systems, and that can't be overridden.

Others (eg, at least a few of the ones in Australia, not sure about the US) have Hertz as the normal owner, but you can override it for a short period - basically just create an account (or login if you already have one) with the toll company, enter the rego and the dates/times you want covered, and you're good! Once the timeframe given ends, it reverts back to Hertz.