I dont work in shipbuilding, but I'm pretty sure how alot of Navy ships at least include stuff from different companies.
Yep.
For instance the current french aircraft carrier was famous for having gone in a lot of troubles over the years and constant drydock because a lot of its components were coming from different sources, like the nuclear reactor being actually a submarine reactor in the first place, or its propellers of US design that never worked properly (the company collasped since then iirc).