Some years ago I had the weather hit 11 dergrees.. Froze the cold water line crossing over from the Curb (Where the pump is) to the Driver's side (Half bath) which is that same type (though a different make) toilet.
Oh, no damage, it froze in the middle of the run and Pex does not mind a bit of freezing and thawing. Now the connections on each END of that line.... Well they were heated so they did not freeze.
So what did I do?
I grabed my 4 cup measuring cup and put it in the sink.. Filled it with HOT water from the sink and used it to "Flush" the toilet.> Worked great
Though I do admit it was just for that one night.