using OSX server in conjunction with Windows server
Yes - servers work well together and you could configure things in just about any manner you wish.

As long as you can map out on paper how you want things to connect, you can configure the server and clients to connect to either or both servers at the same time. You'll have different shares on each server for many cases, but you could have one directory run for both servers so people's names and passwords were centrally managed and not different on each server.