Do all accepted students in top-tier engineering programs get invited to interview before getting admitted?
Not all graduate programs in the US have (official) interviews at all.  In particular, except for Caltech, I'm not aware of any US computer science graduate programs that regularly interviews applicants before making admissions decisions.

There are a couple of sporadic exceptions, which are almost always handled by phone or skype:


Departments sometimes interview non-domestic students to check for English fluency, especially if their TOEFL (or equivalent) scores are missing or borderline but the application is otherwise strong.
Some individual faculty arrange informal interviews with prospective students before deciding whether to offer funding.


Outside computer science, some US engineering departments do regularly invite PhD students for on-campus interviews before admission, but I think this is more the exception than the rule.  In particular, as far as I know, none of the engineering departments at my university (which is highly ranked in most engineering disciplines) do this.