Can the Audio Center serve an Audiotron as well?

I do not know, because I don't know how the Audiotron grabs its files. If it's supposed to get them all from a Windows "share", then no, the Audio Center does not use a Windows Share to serve its files.

However, I'd bet you could hack Samba onto the Audio Center and then it would work. Hmm. That's an interesting idea. Wanna try it for us?

There are details here for information on how to get the Rio Receiver communicating in various ways on the network, and these apply to the Audio Center's server component as well.

Can the Audio Center serve a PC running Windows or Linux?

Yes, you can stream to Winamp with it, for example. Again, details for the HTTP streaming stuff is here.