Answer: Most preformed ponds are so shallow that they do freeze solid in winter and may crack unless there is a pressure reliever of some sort floating in the pond so that the ice can push it up and out as it expands. (A log might do the trick.) Conversely, in some locations the surrounding soil may freeze and thaw and heave or crack a small empty pond, especially if water tends to collect beneath it in wet weather. For the most specific answer about your preformed pond, I would suggest you contact the manufacturer of the liner.
Your water lilies can be kept very cold but not freezing, for example in a bucket in an unheated garage. The other plants can be potted and kept in a sheltered location such as a cold frame or poly house with mulch around the pots to keep the roots from freezing, or possibly an unheated garage. Your main concern with the hardy plants is to protect the roots from freezing, so keep that in mind when you decide where to keep them. In spring when the weather moderates a bit set them outside so they can reawaken naturally as the season progresses.
Good luck with your move!
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