Answer 1: Go ahead, just put it over the T-111 you'll be fine.
Answer 2: Wrap it in house-wrap first, you'll be fine.
Answer 3: Don't overlay, rip off the T-111 and you'll be fine.

There, you got 3 different answers without waiting to have 3 different people post. Your post is like asking the question: Can I pour concrete around my pole barn posts? You'll get opinions on both sides.

Seriously, I'd ask the manufacturer of the hardiplank. They'll know if their product is permeable and be able to provide correct installation procedures. If you have problems later you'll at least know you did it according to THEIR instructions. [img]/forums/images/icons/wink.gif[/img]