Might use the same weight classification. However note the difference in use. CFR49 requires the vehicle use be related to commerce and the IBC does not. So under CFR 49 an RV or a privately owned truck used for personal use would not fall under the definition of a commercial vehicle.
2018 IBC
[F] COMMERCIAL MOTOR VEHICLE. A motor vehicle used to transport passengers or property where the motor vehicle meets one of the following:
1. Has a gross vehicle weight rating of 10,000 pounds (4540 kg) or more.
2. Is designed to transport 16 or more passengers, including the driver.
49 CFR 390.5 (linked)
Commercial motor vehicle means any self-propelled or towed motor vehicle
used on a highway in interstate commerce to transport passengers or property when the vehicle—
(1) Has a gross vehicle weight rating or gross combination weight rating, or gross vehicle weight or gross combination weight, of 4,536 kg (10,001 pounds) or more, whichever is greater; or
(2) Is designed or used to transport more than 8 passengers (including the driver) for compensation; or
(3) Is designed or used to transport more than 15 passengers, including the driver, and is not used to transport passengers for compensation; or
(4) Is used in transporting material found by the Secretary of Transportation to be hazardous under 49 U.S.C. 5103 and transported in a quantity requiring pl
Definition of commerce
(Entry 1 of 2)
2: the exchange or buying and selling of
commodities on a large scale involving transportation from place to place
a major center of commerce
interstate commerce