From the manga, Fog ships are made up of a complex nanite superstructure. The nanites can reform into a ship easily enough... as long as they are still 'alive'. In fact, OTHER Fog ships have shown to be able to use the broken-up bits of nanoclusters to repair themselves or add more functionality (that's part of how Iona gained her new cannon) by absorbing them into themselves. As long as their core is intact, everything else is just window dressing. Even their physical form is irrelevant as long as that core is intact. But the catch is, nobody really knows how LONG the nanites can survive without power - it is never clearly defined in the manga. We know several months is beyond them, but not where the cutoff deadline is.

That said, the real answer is 'Do the writers want them reactivated as part of making a great story?' Gotta love pseudoscience for such things.