Not sure I understand the question.  If it is going to be frozen in at
this seasonal spot then all the same precautions apply as if it was
mobile - still needs to be winterized, don't use the plumbing in the
winter.  Depending on how cold it is the trailer will sweat a little
or a lot so you will need to run the furnace more than you expect
because you will need to keep some windows open to let the humidity
out.  Most RVs don't have a good enough furnace for seriously cold
weather.  -20 F is probably on the extreme end for most rigs.  Some
people obsess about frozen crap - some of us don't.  

We use an electric blanket with his and hers controls for cold nights
and electric space heaters so the park owner pays for the heat.  

Not sure that is the answer you were looking for.