I get the goal behind the payphone idea, but really they just need to turn tips over to CrimeStoppers. Most people trust the anonymity of CS and know they’ll get a reward if conditions are met.
I grew up in rural Iowa. The problem with the phone booth idea is that everybody knows everyone in rural Iowa. I know this isn’t exactly rural- but trust me, it is. Given the history of this case, the rumors of police cover-up, corruption, ignoring leads, etc. Nobody is going to any phone booth there. At any hour on any day. Ever. Because someone, who knows someone, who knows someone would notice that. And mention it. Until everyone else is whispering about it.
Tips either have to go to CrimeStoppers, a COMPLETELY new and separate investigative team, or the NY Times. But you’re right- no known person there is going to reveal themselves or their tip to any person connected to the local popo. JMVHO.