While us "East of the Mississippi River" folks often kid around about tankers versus tenders, as long as those units can haul water efficiently for structure fires we really don't care what you call them. One concern that certainly arises with tenders is the ability for the wildland (forest service) tenders to offload at rates high enough to support a 500 gpm or greater fire attack operation. We have seen a number of off-loading configurations during our travels throughout the United States and Canada and it is pretty clear which FDs plan on using their wildland tenders for structure fire water supply support. Those fire departments have figured out a way to dump that tender's water in short-order and get that rig back on the road for another load.
Therefore, part of a FD's water supply planning process must include knowledge of the water hauling units available in their mutual aide response area and the method by which those water hauling units best offload their water. We all like a 3,000-gallon tender coming to our farmhouse fire, but if it can only dump out of a 2-1/2-inch outlet or pump off at 200 gpm....well, there is going to be a problem. If you have forestry service or private water haulers serving your area, see what you can do to get a large dump or two on those tenders.