Yes, 747-400s do operate at Logan, but you have to almost luck into seeing one. BA, although the schedules don't indicate such, uses their 747-400s on at least one of their three daily flights...yet sporadically. Lufthansa does likewise. Korean Air used to have scheduled 747-400s here, yet terminated that service several months ago. The only carrier that I know of that can be 'counted on' for scheduled 744 service at BOS is Virgin. A quick peek at some of the BOS pictures here will show some interesting 747-400 activity here, including El Al. I believe as recently as last week Air France used the type here one day instead of their normal 2x 767-300s.