If a NS unit that is on BNSF train comes to Denver and the NS unit needs to be fixed does BNSF fix it and bill NS or does BNSF just send the NS unit back to them to be fixed?
There is a code for interline billing between carriers for doing routine running repairs to equipment wherein the owner ends up paying for the repairs that are made. The billing is similar to a mechanics flat rate charge, with specified repairs have a set number of hours and there is a standardized rate for the standard parts that are used in the repairs.
If there are heavy repairs required to the equipment, it is sent back to the owner. The owner will be billed for any necessary ‘emergency’ type repairs that may be necessary for the equipment to be able to be shipped home.
These interline repair agreements apply to both cars and locomotives.
There were/are employees whose job it was to make minor repairs like brake shoes, air hoses and take up slack on brakes for safety reasons. Major repairs are at the discretion of the owner.
A lot depends on circustances, also. If a BNSF unit on NS is in Harrisburg and needs a major repair, it is likely for this case that BNSF will wish NS to do the work at Altoona, rather than have to pay for both emergency repairs at Harrisburg, probably unnecessary or far more limited to get the unit to Altoona, and fund their own major repairs as well. If the same unit was at or near St. Louis or Chicago, it would return home for repair.