The ironic thing is that there should be an electric tow vehicle soon. Tesla is making a pickup truck. I don't know if it will be beefy enough to pull the three-axle, 15,000 fifth wheel up mountains near Denver, but it would be interesting to see.
I don't know how they are going to do it, though. GM gave hybrid drivetrains the college try, and finally threw in the towel this year and stopped selling the Silverado Hybrid.
Of course, if I were concerned about carbon footprint above everything else for a tow vehicle, I'd go for a used diesel pickup (before DEF/DPF), and run B100 in it.