I see that someone has uploaded the scan of the London Codex 29987 -- the images of which are out of copyright under American copyright law, though most libraries will try to claim copyright still. (Though one could almost argue that it took photographic creativity to create such BAD images of a manuscript,

These scans are, btw, more useful than the original facsimile which had the versos (backs of pages) on the front and thus couldn't be viewed in the correct order. Here they finally can be.
I would also urge IMSLP to take a stand on facsimiles similar to the one on PD-Urtexts -- to give a set of time after a facsimile is published in which it not be uploaded (even if the images are PD), the photographing process is quite expensive, and I would think that the publishers deserve at least 10-15 years to recoup costs; otherwise such facsimiles will not be published to be scanned.
http://imslp.org/wiki/The_Manuscript_Lo ... onymous%29
Best,
Michael Scott Cuthbert
(musicologist working on 14th c. music)