Not really. The game's premise is that you're an army officer sent into the Zone to investigate the failure of a mission. It's a pretty natural assumption to think you'd then leave the Zone once your mission is over.
Anyway, COP's story is pretty dumb, and you'll know almost every single facet of it already if you've played SHOC, it's mostly the outside world learning and being shocked by stuff the stalkers already know and are used to. There are seriously plot points in COP that are treated like important twists that you can overhear in bar conversations in SHOC 
"Emissions can create new anomalies!? GREAT SCOTT"
