Whether by design or by default, you'll know tanking is accepted by Dolan based on Fish's job security.
If the team loses massively, and it looks like they might, then Fish's status reflects on Dolan's acceptance of what is happening. If Fish remains safe despite an abysmal season, that basically means Dolan understands this may now be unavoidable which extends to Phil retaining his juice which extends to job protection for Fish.
Anyone can see the roster is bad, but it is even worse for someone who has never managed before to coach it. Maybe Fish will turn out fine. He's not doing great so far, but with this roster most coaches would be damn good to have split the games so far.
If the losses pile up and Fish is still standing, then Dolan accepts the writing on the wall and will not feel the need to make Fish the fall guy. That would be a good sign unless Fish turns out to be really, really bad and a lost cause. Otherwise, it would amount to a tacit acceptance we presently suck and need to land a high draft pick.
The only wrinkle in that seems to be whether Phil planted the seeds in Dolan's head to prepare him for this scenario or not. If he did not prepare him for this, then Dolan's old tendencies may flare up.
And that is the crux of whether or not this is intended or not. If it is, Dolan is already down for it. However, if Plan A was to make the playoffs and attract a top FA, Phil had to already know we might suck and tanking was a very good Plan B.
If Phil pre-sold Dolan on Plan A + Plan B, then nobody will pack their bags whether the tank is planned or not.