m3u format

In general, yes.

I am GUESSING that it might be possible to “back into” some common path internally, and then to paths to go across disks, something like:

From Server 1:

…/…/servername2/share/path…

but that would require expirementation to determine what WD’s internal paths are.

One thing to try is to look at the PATHS that are shown when you bring up the OPTIONS menu when playing back video files.  (I can’t remember if audio files show the path when doing that.)