Well I know many of us appreciate your experience and the time you take to answer questions and contribute here!I had to give up keeping rabbits several years ago, due to mobility issues.
Yes, the rubber bowl would freeze, but it was larger and the rubber seemed to insulate it better than ceramic. It's also unbreakable. I used to just turn it over and step on it and the ice would pop out. Then I'd refill with warm water. I found that the rabbits enjoyed the warm water, so even though it freezes a bit faster than cold, I gave it to them that way.
We get cold snaps well below Zero F, but they rarely last more than a few days at a time. But it's a rare night from mid-December to the end of February that temperatures don't dip below freezing.