I've done OK in an environment where daytime temperatures were 40-50 F, night temperatures in the high 20s for a few hours. However, all of my fresh water tankage is in heated space, all of the fresh water plumbing runs are either in heated space or immediately under the flooring and still insulated from outside temperatures.
My waste tanks (with heating pads) are in unheated space, but whether or not contents are frozen does not matter until it is time to dump. I dump when I am in someplace warm enough.
I know nothing about the plumbing of Shasta RVs generally, and I suspect it is different model to model, as it is for other brands. This is something you need to analyze yourself, what is in heated space, what is exposed to sub-freezing temperatures, and how long will those spaces be subjected to freezing.
This is assuming that you will be running your furnace full time, to keep living areas at comfortable tempatures, so that heat loss will keep utility spaces above freezing most of the time. If you are not going to be running your furnace, it is best to winterize, and use the RV in winterized mode, which for most designs means no running water.
