The Buccaneers had a plan on offense in 2009. They were going to go with a powerful running game, and a deep play-action passing game. They brought in Jeff Jagodzinski to carry out that plan, but that was a failure and the coach was fired before the season began. Greg Olson was left but barely had time to implement his own scheme, leaving the 2009 offense directionless and ineffective. The 2010 season was very different, as Greg Olson's game plan and Josh Freeman's qualities as a passer combined for a potent and dangerous air attack. Despite handing the ball off to Cadillac Williams again and again, the Bucs couldn't get a running game going early in the season. It wasn't until Blount came in that the running game started to work. So how did the play-action based deep shots work if the Bucs couldn't run the ball?
The answer is very simple: they simply ran the plays, and opposing teams acted as if they needed to expend extra effort to stop the run. Defenders are conditioned to react to their running keys and get up in run support when they see a running play coming, and that doesn't change whether the opposing running game is any good or not. Whenever the early-season Bucs ran play-action, every opposing linebacker stepped up, and the move was effective - without any running game. The key to a succesful play-action-based passing game isn't running the ball a lot and effectively. The secret is to simply execute the plays as designed.
That's not to say that a good running game doesn't help a passing game, though. It absolutely does. You could see that when the Bucs played the Redskins and they were forced to move 8 or 9 players into the box and blitz on every down to stop that devastating running game. The Redskins were simply not good enough to take advantage of the holes in the Bucs' coverage, but that running game. definitely forced the Bucs to compromise their pass defense. That's what a good running game will do, but it won't have much effect on the success of play-action.