I've seen "Windows Services for UNIX" which made use of the Microsoft POSIX subsystem actively for both access to filedrops on older UNIX mainframes NFS shares to ports of software that I ended up having to maintain for some time. It was used enough for it to appear a few times in my consultancy work in both private and public sector.
Edit: If you want to discuss this further, we should start another thread so we don't go too off topic here. My original post was meant to be a bit of humour.