I'm sure it isn't, but then again because there has been no Warden of the island in a long time, so who knows?  Remember though the original creator and most likely Warden was Merlin, himself, he would have the tools to get them too the island... But leave no doubt from the degree of Mab's fright as Alfred moved towards her, he is capable...  She is almost as powerful as any of the monsters in the place already.

There is at least one WOJ where he has stated categorically that Justin is dead, with an emphasis on DEAD.  However, as established especially in Dead Beat and Ghost Story, being dead does not necessarily mean you are out of the game.

I find it very unlikely that a schemer like Justin would be caught without a backup plan.  Elaine was in Justin's thrall for quite some time.  Plenty of time for him to prepare her in some way.

1: Justin could be riding along or controlling Elaine, a la Corpsetaker.  She might be aware, or not.  He could be hiding in her subconscious and only controlling her when she sleeps.  Justin could have informed the RCV then.

2: Justin is a spirit, a la Evil Bob and Kravos.  He was well versed in necromancy.  He could have communicated to the RCV through an Ectomancer (I doubt Mort is the only one of those).

3:  Justin used necromancy to make himself into a litch.  Harry said, IIRC, that Cowl's magic felt somewhat familiar, but dark and twisted.  This seems to fit.

I agree. I have used this passage to support my theory that Justin is not dead, and further is in fact Cowl. I am sure I am not the only one. For more reasons than I care to name right now, it is very likely Justin is not gone. The books have put some emphasis on the distinction about being dead and being gone.

I may rewrite that theory when I am a tad less busy but yes I think Justin will return to the stage, one way or another.

I wouldn't be surprised at the Reds directly suppressing or containing some kind of big nasty. There's plenty of precedent that the monsters don't like competition in the DV.