I know the question has pretty much been answered, but I’ll throw an additional 2 cents into the pot.
Given the recent barrage of ads about NASCAR coming to ESPN, I think ESPN is using this week to broadcast additional NASCAR-related coverage leading up to their inaugural broadcast (at Indy) on Sunday. NASCAR Now is usually on ESPN2, but they moved it to ESPN during the ATH/PTI slots to give it more exposure this week.
I assume that NASCAR Now is only in that time slot for this week, but I thought I recently heard an ad on ESPN radio for PTI with Michael Wilbon saying (paraphrased): Join us for the return of PTI on Monday, July 30 at 6:30 Eastern, which made me think that NASCAR Now might fill the 5:00 slot for the remainder of the NASCAR season.
ETA: ESPN.com’s television schedule lists ATH and PTI in their normal time slots for next week.