I think you could call me an expert on trucks and oil/gas field work. I worked nine years in the Gas Patch in western NY, PA, and Ohio. Water trucks were always emptying brine tanks at producing wells, rig moves, frac and cement jobs, wireline trucks, power tong trucks...etc..etc..
We had over 30 IH dozers from TD-8's to TD-20's. For water truck support, 95% of the time a TD-8 with a winch hauled on a tandem tilt bed would be the main tow tractor. An old 450 JD weighs about 8 tons and with a winch and good track pads will handle almost everything you need. If the loaded truck stops when starting to get in trouble, no problem for that size dozer. If its bad, we would get a TD-15 or another TD-8 to come help out. On rig moves with very heavy loads, we would use at least two 15's or even a 20 or two. Our access roads were always built bare minimum and trucks put through hell at all times. I have a 450C and that machine will relay pull. If you have oilfield bumpers on the trucks, well thats even better, because you can push, pull, spin them around in slick ground with the blade, etc. We only winched them if we could not push them through slick spots.