We did a Yosemite trip over the new year, I don't know for sure how low the temps got but it was probably mid to high 20's. I put a little anti freeze in the grey and black tanks. I have to admit, I didn't think my hose would freeze, but it sure did so the next day (and the rest of the trip) we used the fresh water tank...silly mistake, but no damage done.
We ran the furnace and kept the temp at 65 or so and were just fine.
No reason to park this RV for the winter, it does well in cold weather.