The Emission Control Interface namelist is meant to provide control over emissions scaling for files that are provided to CMAQ for input. If your onroad emissions are already lumped in with other emission sources (e.g. agriculture, cooking, solvents, etc.) then you will not be able to scale them separately.
If you have onroad mobile emissions in their own file, but exhaust and brake/tire wear are not separate, then you can scale them separately by creating rules that modify the ‘ALL’ selection under the stream column to just specify the mobile source file. You can view the tutorials here to get a better idea of how this would be done: CMAQ/CMAQ_UG_tutorial_emissions.md at master · USEPA/CMAQ · GitHub
In your case, the brake-tire wear factor will be mostly affecting the coarse mode while the exhaust factor will be mostly affecting the fine mode, so you may be able to get away with scaling these different components from the same mobile input stream.
If you have mobile exhaust emissions on one file and brake/tire wear on a different file, then you can scale all emissions from each stream according to their specific factor and you will have a better representation of the impact of the change.