Hi Bob,Even down here, I have kept young fig trees in pots the first few years, those Celestes included when they were babies. The weather is so changeable that it's easier to protect them if they are in pots.
If you mean my regular Celestes, one is in-ground and one is in a raised planter frame my husband built for it and it has no bottom on it, so I guess that's the same as in-ground.
I have an Improved Celetse growing in a pot for now and just got an O'Rourke (hopefully) which is also in a pot.
When we had the icy rain a few weeks ago, the Celeste out front in the frame and the one out back in the ground sat there coated in ice, just a-smiling away. It didn't even kill the nice green bud tips of either one of them, but it didn't last for days. Don't know what would have happened if that were the case. We had some low temps and the bud tips were fine, until I chopped almost all of them off in pruning back both trees. The ones that were left are leafing out nicely and the wood is popping out buds, as well. They're just appearing out of nowhere.
It's the heat that gets them down here, or warm weather in the winter that gets sap flowing then a freeze, which will split the trunk and branches. Even when that happened to a different Celeste I had years ago, it didn't kill the branches, or trunk, it just left little split marks all over the tree. The tree healed itself. I took a knife to the places and shaved away the bark, then put tree paint over the areas, but only on the main trunk and large branches.