glacier-cli currently relies on a local cache of
inventory information, and so other git-annexes using the same glacier
repository are not able to access stuff in it, unless and until
glacier vault sync is run.
An example of this causing trouble is with the assistant. When a file is moved into archive/, the assistant that sends it to glacier is able to trust that it's in glacier and remove the local copy. But other assistants that also have a copy cannot trust that, and so don't remove their copies.
I've discussed with glacier-cli's author making git-annex store enough info in its branch to be able to bootstrap glacier-cli to know about a file. This seems doable and he had a design; waiting on movement on the glacier-cli side.