If they do not have a License To Carry, then they cannot carry a handgun in your vehicle. It must be a vehcile they own or in control of.
Here is the whole bill(2) inside of or directly en route to a motor vehicle
that is owned by the person or under the person's control.
http://www.legis.state.tx.us/tlodocs/80 ... 01815F.HTM
A long gun can be carried by anyone as long as they can legally posses it.