(a) A toll project entity may establish a discount program for electronic toll collection customers. The program must include free or discounted use of the entity's toll project by an electronic toll collection customer whose account relates to a vehicle registered:
(1) under Section 504.202;
(2) under Section 504.315(g); or
(3) by a person who has received the Medal of Honor.
(b) The legislature may appropriate funds from the general revenue fund to a toll project entity to defray the cost of providing free or discounted use of the entity's toll project under this section.