The received wisdom of yore is that it's easier to port code from one language to another than to rewrite from scratch. However, I suspect in practice most people who do that will wind up rewriting in part and that's where the pain happens, screwing up all the undocumented edge cases.

In this day and age it generally makes more sense to keep the codebase in the original language and use virtualization as required to keep it running without the human overhead of porting.