actually, it was all on the BOS app/dep feed. There are a handful of sectors on that feed, and AAL1535 remained on the frequencies that are scanned on that feed. If you select the 1200-1230 (local time) archive, you'll hear AAL1535 ask for vectors back to the airport about 2-4 minutes into the archive. You can check out www.passur.com
to view radar data overlayed on a topo map. I went back to 12:00 so I could see the flight on-screen and listen to ATC at the same time.
As far as the scanning intervals, usually the scanners cycle through the frequencies very rapidly until they find one where there is a transmission. They stay on that freq until the transmission is done and then continue scanning.