afrag is correct here. It has two great uses.
1. If your opponent has a powerful outpost in play, you can return that outpost to their hand so you may attack them and their regular bases (assuming they have no other outposts).
2. You may use the ability(s) of one of your bases, then return that base to your hand and replay it. The rules treat any card played from your hand as a new card, so you may again use its ability(s).
Does that mean that you cannot use Battle Barge against an opponent's non-outpost base if he has an outpost?
Can you use Battle Barge against your own non-outpost base if you have an outpost?
This thread asked whether you could apply "destroy target base" to yourself - and whether you could destroy your own non-outpost while you had an outpost.
(I suppose that someone will eventually ask whether you can destroy your own bases with combat.)