— Tim Graham (@ByTimGraham) March 25, 2014
It's a relatively common practice in the NFL; practicing with the enemy. The Vikings and Chiefs have conducted live scrimmages against each other for years, and the Patriots and Buccaneers have done it recently.
The Steelers haven't, but according to Buffalo News reporter Tim Graham, they are discussing a joint-session this upcoming training camp with the Buffalo Bills.
The two teams often meet each other in the preseason; the league sets its preseason schedule based on which teams want to play each other, typically due to familiarity. Having dual practices and live scrimmages couldn't hurt in a fundamental sense. The Bills and Steelers are not scheduled to play each other during the 2014 regular season.
The Steelers defeated Buffalo 23-10 last season in Pittsburgh, with neither team making the playoffs. They met in the preseason in 2012 in Buffalo.
According to Brian Galliford of Buffalo Rumblings, "...the Steelers are about 214 miles away from Buffalo (and vice versa), only an extra 25 miles between Buffalo and Cleveland."