In these places we wouldn't call it a "policy" but just how we did things.

One of the devs there was talking to someone about "implementing any calls in .NET" as NetMQ (native ZeroMQ for .NET) using an exclusive pair socket to pass Apache Thrift back and forth to Rust codebase also using the exclusive pair socket. One of the phrases I heard was "all code we contribute is accessible to your existing .NET devs".

The term accessible may not mean readable or maintainable for the .NET devs in that context, but the corporate customers seemed comfortably confident they would continue to have a relationship with the firm so whatever.