Emerson made two claims in court, reading the below first claim implies you need consent to use the trademark. I don't know what law specifically, but it is mentioned in general below (per above linked article). The defamation is another matter.

"In the lawsuit, Emerson claims that NBC used Emerson's trademark without the company's consent..."

I say it's a gray area and to be careful that's all I am trying to impart.

If one wants to make a US released coffee table book (photo book) of all the 2011 John Deere tractors (logos and mention of John Deere) just don't be surprised if there is a knock on your door.