The right way to update as a sub contractor

Dear All

I have one question here. we as a sub contrauctor, using a whole program along with main contractor and other sub contractors (Baseline issued to us is the program issued by Engineer for the whole project including main contractor and all sub contractor's activity)

When we update the program, we will update our activities but we can't get the right expected completion date of project because we can not update other contractor's activities which link to and will drive our activities (in critical path).

So, my questions will be:

1.How to update the program and get the right outcome as a sub contractor in such a condition?

2.When we receive design change, we will have the event inserted into baseline and get a delayed program, But since we can not get a exactly updated program every single time after we receive Design change from engineer(impossible to require every parties to update the program), how to get the right EOT?

Appreciate for your advise.