(a) In addition to the operation authorized by Sections 551.453 and 551.454, the governing body of a municipality may allow a motor carrier to operate, for the purpose of picking up or delivering mail, parcels, or packages, a vehicle bearing license plates issued under Section 551.452 on all or part of a public highway that:
(1) is in the corporate boundaries of the municipality; and
(2) has a speed limit of not more than 35 miles per hour.
(b) In addition to the operation authorized by Sections 551.453 and 551.454, a county commissioners court may allow a motor carrier to operate, for the purpose of picking up or delivering mail, parcels, or packages, a vehicle bearing license plates issued under Section 551.452 on all or part of a public highway that:
(1) is located in the unincorporated area of the county; and
(2) has a speed limit of not more than 35 miles per hour.