I'd suspect somewhere in the contract between Nine PBS and OSS there's some wording about what happens in the event of OSS discontinuing operations that doesn't include the words "silently fuck off into the woods without informing customers," which appears to be what happened here.

I agree that IM is probably inside of their contractual rights, but they're still handling this in a fashion that risks causing severe issues for Nine PBS. The presence of the court order seems like sufficient inducement to at least hold the deletion until the court decides, and I'd be very curious what kinds of legal remedies Nine PBS might be entitled to should IM not do so and the court decide in their favor.