I am sure some people can. I got pretty far in the interview process at xAI, but couldn't get anyone at other AI labs to even reply my emails, though...
(I dropped out at the end because there were issues with HR not wanting to hire in certain geos, and me not wanting to relocate to the USA or London)
xAI is a pure choice. Their people have the ability to work at Anthropic but choose xAI.