What is the ruling on working for a governmental investment authority that invests funds abroad?

There is no objection to working for an organization that invests its money in interest-based banks, as long as its operations are permissible. This is because the lease contract between you and them is for a permissible matter, and this falls under the ruling of dealing with someone whose money is mixed with lawful and unlawful sources, which most jurists do not forbid. However, if the organization deals in impermissible matters such as usury or selling prohibited items, then it is not permissible to work for it.