Bill Belichick enjoys the preseason as a time for unorthodox coaching. His joint practices have become a tradition where he's able to bestow his wisdom upon other teams (generally his former acolytes), while he receives a chance to pit his players against some real talent.
It's a sort of jacked-up practice to make-up for the new CBA and the lack of real training time over the off-season.
He's worked with Chip Kelly, Thomas Dimitroff, and Greg Schiano in the past. This preseason, we have the following line-up:
Week 1: At Washington
Week 2: Vs Philadelphia
Week 3: Vs Carolina
Week 4: At New York (Giants)
You'll note that the team isn't going too far. Washington is only a short flight away (heck, they could even take an early bus and get there before lunch). Their opponent of the furthest distance is Carolina and they'll be coming up to Gillette.
It's likely the Patriots will be holding joint practices with Chip Kelly and the Philadelphia Eagles, just like last season, and I wouldn't put it past Riverboat Ron Rivera and the Carolina Panthers to be another team of interest.
The Patriots will be facing NFC North, so there isn't a crossover in scheduling.
You also have to feel bad for the Cowboys. How come they didn't get the NFC East invite?