I googled around and read the forums, from what I gather this is both possible and impossible. I think older versions of NGUI anchors + tween was impossible, newer versions it appears possible.
So I have a setup like this, basically a big container for buttons.
UIRoot
-Camera
--Panel
---ContainerMain
----ContainerButton
-----Texture
ContainerMain is anchored to Panel.
ContainerButton in anchored to container main.
I have two TweenPositions set on ContainerMain, one to slide it in and one to slide it out. I fire the tween in script.
This is where it breaks down. This breaks resolution independence. The anchor does its job but the tween seems to work in absolute numbers.