> I'd love if someone still working there were to write a nice post about that system, it was the first of such a kind I saw.

I don't know how far back you saw the Bloomberg system, but at this point it's basically the same as the Debian system (as in, debian/ subdirectories, .deb files, etc.). Versions of git projects are published as tarballs (source packages). Then sets of published projects are "promoted" and all projects that transitively depend on them are rebuilt and unit tested in a sandbox environment. If that process fails, the promotion fails.

Each source package can use any number of build systems, implementation languages, or project structures.

There's also a legacy subversion monorepo with a monolithic build system that builds on top of that, but it's slowly being phased out.

All that is an integration build including thousands of discrete projects. Those projects typically have additional CI/CD enrollments outside of the integration build system too.