Try reading it this way:

"(awards) or (assignments to any vacancies or surpluses) posted prior to SOC will be restricted to pilots within their respective pre-merger fleets."

I see it as, the company cannot post the awards or the assignments prior to SOC that affect the whole pilot group. You should read awards or assignments are the two options.

If the TWG meant the way you were thinking, I think it would say, "Advanced Entitlements" rather than "awards/assignements". We don't call the advanced entitlement an award - it's an Advanced Entitlement.