In the best case you might have all the engineers rolling up to the same line manager sitting in the same office, but those above entry-level are expected to spend a good portion of their time collaborating across teams (and therefore across sites).
Varies quite a bit by company. Pre-pandemic, we had phones in our cubes :-) Thus I could easily turn Teams off. My immediate team was physically nearby, and people elsewhere could email. They'd call if urgent.
