[eluser]InsiteFX[/eluser]
Ok, I am not really sure how you would handle this, because the CodeIgniter index.php loads all the CodeIgniter core and libraries it needs then it takes control and runs the default controller.
I do know that some users have taken libraires and modified the to be stand alone.
I think the conflict may be because both files are named index.php, but not sure.
You could try this, I sure that you need the full site path.
Code:
include("http://your path that shows when you go to your site/ci/index.php");
InsiteFX