I have no idea. Shutting down preventatively would be smart, and they had good leadership in their IT space while I was there. Friendly people who could make the hard decisions quickly, weren't afraid to pick up the phones to call people, and supported the growth of struggling employees without letting shoddy work get approved. They were also good at managing large multi-year and nation-wide project campaigns - a rare skill in this world.
That said, determining whether or not a system was compromised can be incredibly difficult. I'm sure they'll face massive pressure to turn the pipeline back on as it does supply almost half of the east coast with oil. I wouldn't want to be the person who has to make that call when it's impossible to prove a negative.
CPC had two explosions a few years back which caused gasoline shortages in new england, that may provide indication of the scale of disruption to expect.