This arrangement makes a lot of sense for both teams, and that's why it isn't out of the question to think this could become an annual family reunion with the Harbaugh brothers.
The ideal situation is the Ravens and 49ers holding combined practices with their NFL neighbors. But the Ravens and Washington Redskins haven't arranged an informal scrimmage since 2007, perhaps because of their battle over territorial lines and fans in Maryland. The 49ers and Oakland Raiders haven't always been willing to work together in the past, and they haven't played a preseason game since violence erupted during and after their August 2011 meeting at Candlestick Park.
The key to these joint practices is finding a common ground on practice structure. What kind of drills will be run? How much hitting will be allowed? Can teams control their players so punches aren't thrown and hits on quarterbacks don't occur? This isn't expected to be much of a problem with John and Jim Harbaugh, given the fact they even share the same team mantras like "Team, team, team" and "W.I.N." (What's important now). These practices also allow their father to watch both of his sons' practices and serve as "unofficial official."
The Harbaugh family will enjoy the rematch of the Super Bowl more than some of the players. Wide receiver Anquan Boldin hasn't faced the Ravens since being discarded for a sixth-round pick. Ravens linebacker Terrell Suggs and 49ers offensive tackle Anthony Davis may have lingering bad blood after Suggs insinuated Davis was a "fake tough guy" and Davis responded by calling Suggs an (expletive) "loser."
This is the first time either team has held combined practices in their Harbaugh eras. Joint practices, though, aren't anything new. The Pittsburgh Steelers and Buffalo Bills have a two-year agreement on meeting in training camp. The New England Patriots, who have conducted several joint practices over the years, could work out against the Philadelphia Eagles this year.
Combined practices will become even more popular if the NFL reduces the number of preseason games. Teams still need to evaluate their players, and these combined practice sessions would help offset fewer games. It's good foresight to establish these relationship between teams now.
If everything goes smoothly this summer with the Ravens and 49ers, it would be beneficial to both teams to make this more than a one-time family affair.