heavy guage harness with a push to start?

If i understand you correctly, most PTS cars are controlled by the BCM for the start sequence. Since all have some type of immobilizer also, it only makes sense to use a bypass module that will also deliver data to control the PTS. Idatalink makes modules to do this on most PTS cars.

So, to answer the Q, it depends on the type of car but most times the heavy guage ignition wires aren't used to actually start and run the car, the data module does.