Sharing photos.app library across multiple machines I have three machines: A Mac Pro, a Macbook Pro and a Macbook Air. I created the library on my MBP and all photos are stored on the file server on my network which all machines can access.

Copying the library to my MBA and MP, I can see the thumbnails as you'd expect but it refuses to load any files whatsoever, despite the volume being mounted at the same path.

Has anyone had any success in getting this to work?

I had a look at the database and each file has a hex encoded string stored against it which is storing system disks UUID amongst other machine specific things regardless of the fact that it's on the network share.
According to this Apple Support Document:


  Important: If two or more users attempt to use the same iPhoto library
  and the library is not on a volume where permissions are ignored,
  unexpected results may occur. This includes the inability to see or
  edit certain photos, or the inability to open the iPhoto library.
  Follow the steps below to ensure each user has read/write access to
  the iPhoto Library.


Essentially, a single Library must reside on a volume where permissions are ignored. A NAS or a shared internal/external non-System HD attached to your Mac Pro be a good start. You will not be able to share the Library from the internal boot drive as it cannot be set to ignore permissions.