I've now read in detail the "meat" of the lawsuit filed by Cumulus. I more or less agree with K.M.'s assessment in terms of the Tying allegations.
As a result, I rescind the following comment I made earlier:
Cumulus has little chance of prevailing if this goes to trial.
If Cumulus' depiction of the facts is indeed accurate, they likely have a strong case against Nielsen in terms of the Tying Policy. Nielsen prices national ratings data very differently (i.e. much more steeply) for network syndicators who also operate local radio stations than for network syndicators who do not operate local radio stations. The primary way to avoid the absurd differential in pricing for national ratings data is by purchasing local radio ratings data in a multitude of markets regardless of the actual desire for such data. Another option is to accept a "Swiss cheese" style national ratings report whereby Nielsen intentionally excludes data from the local markets where the standalone local market reports were not purchased.
Under U.S. Anti-Trust law, if the provider of a desired service has monopolistic power over said service, it is often illegal for that company to coerce a customer of the desired service to also purchase an undesired service. Based on Cumulus' version of the facts, it certainly appears Nielsen is engaging in such practices.
On the separate topic of the Subscriber First Policy, I think the case presented by Cumulus is much weaker. They are essentially arguing it should be mandatory for Nielsen to publish the ratings data of all local stations in the ratings report for that particular survey area irrespective of each station's subscription status, since failure to publish such data could result in ad agencies not doing business with the unlisted station(s). It is unclear to me why Cumulus believes it has a right under the law to dictate the level of information Nielsen chooses to present or not present to its paying customers if Cumulus is not paying for the service in question.
Let's not lose sight of the fact Nielsen is choking on $11 billion of debt from its 2022 take private transaction. If Cumulus were to prevail on its lawsuit, the result might not be much of a price reduction for national ratings data for Cumulus (Westwood One) and iHM (Premiere), but instead, a big price increase for other companies that might use that data to bring everyone to parity.