If you play Emptying the Hold:

Action: Search the top five cards of your deck. You may put into play (in any zone) one unit found amongst those cards with printed cost 3 or lower. Then, shuffle your deck.

So if you get a Battlefield only card, can you play it in any field?

FAQ:

"“Put into play” means that the card enters
play through a card effect instead of
through normal costs and restrictions. An
important distinction is that put into play
does not bypass the unique restriction or
any restrictions in the text box of the card."

Second sentence indicates those limitations still need to be adhered to.