Using 2.12 we were able to broadcast featured images from custom post types in our wordpress network, however it would not store the image if there was an image with the same name on the receiving website. It would show the existing image in its place.
Updating to 2.15, there is a new bug.
The issue we were having in 2.12 appears to be fixed. It is trying to store new images even if there is an image with the same name. However the image itself is broken or missing, it hasn't been broadcasted properly.