First, What's OCC? Second, if flow control comes from ATC how can times be adjusted based on connections and crew time? That has nothing to do with ATC.
Operations Control Center (OCC) is the ops nerve center for USAirways. It's not like at most regional airlines, where there are a couple of dispatchers and crew schedulers who are underpaid, overworked and inexperienced.
OCC in PIT is pretty amazing. There are people in OCC who's primary job is to work with Central Flow...(flow control and wheels up times)
When Central Flow institutes a program (every day) OCC works with Central Flow to try and keep everything running semi smoothly. OCC may swap out one flight's slot time for one that may need to get to the destination for what-ever reason..(international connections, mx, crew times, anything really)
It's a lot of wheeling and dealing and OCC does an excellent job with it. The Shuttle is a prime example of the wheeling and dealing.
Since the commuter slots are low on the priority list, they usually receive the short end of the stick. (most flow)
So in a nutshell, OCC can persuade ATC to adjust flow times due to anything OCC deems neccessary.
And on an added note, the envasion of the RJ's over the past several years to the North East's airspace has caused the flow problems. 10 years ago, flow control programs went into effect for wx, not for traffic. Too many airplanes in the sky!