Well....I did this..
From my laptop Builder, I 'mounted' the drive I use for my operational Premise '\\BREAKWATER\Music' as fileprovider one (#1).
I created a second fileprovider (#2) using music from my laptop 'C:\Users\Public\Music' (I just got this laptop in the last month - boy do they put some junk on as example music!)
Results?
The mounted drive (#1) didn't provide any metadata...the first time
the local (#2) did
I copied some of the files from case #1 (mounted). Imported them in as fileprovider three (#3). No surprise. Metadata!
But wait!
So I closed the builder, reopened and added another NW share (#4). Metadata!
I thought, 'Am I on crack?!'
So I added another NW fileprovider (#5). Metadata!
Works as designed. Sorta...
The one odd behavior I saw is I was not able to force a NW fileprovider to redo a search by deleting/adding a file extension (normally, if you delete or add a '.bmp' or '.mid', or other extension, it forces a search)
Scan/no scan didn't seem to make a difference, either.
So maybe the best suggestion I can offer is to copy some to a local drive, see if you get any metadata. If so, then we can look at something else. What, I have no idea.
Folk? I guess if thats what you like to listen to...