Maybe a third to a half are Mozilla employees (although it's infamously hard to tell who actually works at Mozilla and is just weirdly into maintaining Rust).
FWIW, the Rust-push team doesn't match the set of reviewers (people to which the integration bot bors will react and merge a PR). Being on that list offers powers like issue tagging and the ability to push to the 'try' branch, but manually merging a PR or pushing straight to master is essentially banned (and would be reverted immediately).
There is an injection from the set of reviews to the rust-push team (Or, at least, there should be), but e.g. people have got privs because they've been doing a lot of triage or need try push, without having review powers.
Maybe a third to a half are Mozilla employees (although it's infamously hard to tell who actually works at Mozilla and is just weirdly into maintaining Rust).