Yes! Find the solution! Pls, Tynan don't kill me for this kind of code! I hate reflection but somtimes it's the fastest way...
CompFacility t = TargetA.Thing.TryGetComp<CompFacility>();
List<Thing> l = (List<Thing>)t.GetType().GetField("linkedBuildings", BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static).GetValue(t);
l[0].Property_I_Need_To_Set = my_value;
CompFacility t = TargetA.Thing.TryGetComp<CompFacility>();
List<Thing> l = (List<Thing>)t.GetType().GetField("linkedBuildings", BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static).GetValue(t);
l[0].Property_I_Need_To_Set = my_value;