P&W has an extremely limited interchange with CSOR. Not sure what exactly they're allowed to swap, but they are so constrained that CSOR will always have to remain in a different realm no matter how much NECR and P&W start integrating over time. The CSX paper barriers cover all the ex-Conrail territory that CSOR took over, so vast majority of their business is bound up in the CSX interchange. Think they've got a little bit bound up in Pan Am Southern, too, for the small section of Armory Branch they own/operate.
The only real integration the P&W acquisition into Genessee & Wyoming is going to afford CSOR is that P&W can deliver equipment door-to-door to them at no extra charge from their own engine house in Worcester or via NECR interchange @ Willimantic. Before now PAS had to be the middleman on any NECR-CSOR rolling stock swaps. Should lower their costs a bit since their power pool has always been shared with the bigger G&W roads. Will give them access to P&W's full-service locomotive shop for inspections and repairs, which will take some overhead off Hartford Yard. And should give them access to more & better MOW equipment because P&W has a sizeable work roster of its own and lots of lend/lease ability with CSX, MBTA, and Amtrak in Worcester since their shop takes on a lot of small outsource tasks from those other carriers.