One has to be careful with how many TVS diodes are across any individual track if you run any DCS locomotives. Each TVS adds significant capacitance across the power that can and will degrade the DCS track signal. If you have half a dozen across the track, it's a significant factor.
If you're really worried about the effectiveness of the TVS, put one in each locomotive, the absolutely best place for EMI protection is right before the protected electronics.
