when a model with the skill impersonation 2 deploys against an alien army, passing its wip roll, does it deploy in impersonation state 1 or impersonation state 2?
You need only pass a WIP roll when attempting to deploy your impersonator in the enemy's deployment zone. Whether you do this and pass or opt to deploy normally, a model with Impersonation Level 2 will deploy in Impersionation-1 state regardless of the opponent's faction. Please note that Spiral Corps counts as a Human faction for the purposes of Impersonation.
By “may be used to impersonate a species alien to the user”, they mean “can adopt Impersonation-1 against anyone.” That’s really all Impersonation Plus changes, like Xeurian wrote.