Per @Siropu in a previous post, it can do this. I have not used this feature, but it I believe it can do what you are asking based on his comment previously. He did not specify subdomains, but my guess is that this would be covered under the external usage. From this update, this functionality was added:
I'd personally recommend working on your ad setup on a test installation to get a feel on how it works before changing anything on your live site.
It does not, at least not in my experience. If you've got ads running using XF's system, those aren't touched since this addon builds it's own positions. Best practice would be installing this addon on and creating ad packages to systematically merge your old ads into the new system.
Thanks for the reply.