It would be handy if it could. I use both mellel+bookends and latex for different things I'm writing, so I need to have my library in a .bib file that works straight away. But I guess it's tricky to implement this, and not very important for all bookends users.
Just so you don't think you're alone, I also use BE with LaTeX, and the more automatic the process of using the exported .bib file is, the better. So this request has a second, though I readily admit that I also don't know how feasible it would be.