Basically, the info has a certain amount of value, that doesn't really go down. If you pair that information with the knowledge of when it will be published, it goes up in value.
I was thinking of the value of the news to Bloomberg, which was mentioned in the article:
At Bloomberg, scoops about deals are highly valued, because beating competitors like Reuters or Dow Jones helps to justify the high price of a terminal, which carries rich veins of data along with news, at a reported cost of around $24,000 a year. The terminals constitute the company’s core business.
If the information is deemed important, then, as soon as Bloomberg is confident in the information's accuracy, it will publish. Once Peltz had a record of giving reliable tips, that would likely happen quickly.
The feds may well, of course, have independent non-circumstantial evidence of the journalist informing Peltz about when the information would be published.