What are the feed addresses for “recommended sites” feeds in Instapaper

I use Google Reader and Instapaper, and I have a pretty good understanding of rss feeds, and have spent a lot of time finding feeds that are appropriate to Google Reader.

I use Instapaper mainly for articles I come across in my feed reader, but I recently discovered that Instapaper has a "Browse Recommended Sites" options where you can add certain content to Instapaper directly. It would be great to basically have a free subscription to the New Yorker, the Atlantic, The Economist, where all of the best longform articles go straight into Instapaper…my question is, what are the rss feeds that Instapaper is using to get that content directly in?

For example, if you look at the Atlantic website, and go here there is no rss feed that says "Long Form Content from the Print Edition." You can only subscribe to individual writers or channels.

If you look here on the new yorker website, there is a feed that just says "The New Yorker" at the top, but then how do I know if that's the exact same feed going into Instapaper? If that's the case, and Instapaper isn't optimized for general feeds, why would Instapaper recommend a general feed like that they may not contain 100% long form journalism?

I want to know if Instapaper is curating their own feeds using some sort of software like Yahoo Pipes to sort for just long form articles,

or if they have a special agreement with some of these sites to get a proprietary feed,

or if there's a way to find out the exact rss url that Instapaper uses for those recommended feeds,

or if someone could at least direct me to the feeds that Instapaper is using on The Economist, The Atlantic, The New Yorker, Wired, Vanity Fair, and Newsweek.