Can you point us to where they said the Dungeon Keeper game is based on the UO 3D engine?
If you look at other games they have, then you'll notice that they're all kind of the same.
So it's a fair assumption that they use the same base engine across games, kind of like Bioware (Aurora, although I think Bioware recreated Aurora based on the UT3 engine for Mass Effect, and each iteration has s different name) or Valve (Source).
So similarly it would be fair to
assume that they will share an engine.
But, as I've said, there isn't any news, so it's all speculation.