You can't save as a p3d in any program except O2.
What you can do however is saving it as a .3DS file and import that into O2.
I don't know if Maya can open .abc and .dtx files, they seem like proprietary formats, but I think Milkshape 3D can open AvP and AvP2 models, and I know for a fact that it can save to .3DS format.