Not sure what's causing the problem, but I've determined a better solution for what I'm trying to accomplish:
bower install git@bitbucket.org:username/my_repo.git --save
So I'll just be using bower for sharing stuff between repos. I didn't realize you could use a git repository url for a bower component. Pretty sweet I say. Unfortunately this doesn't allow me to make upstream changes from the repo I'm using, but at least I have a super easy way to do it :)
Update
I posted this method on Google+ and Rob Becker mentioned that you could make it even simpler by using a bower symlink:
Try adding in "bower link" to reduce all that copying.
You can simply have your shared code in separate repos and set up as bower components as you already have. Then do
$ bower link
in bs-js-common
This sets up the link. Then in your main project where you have a bower dependency on bs-js-common just do:
$ bower link bs-js-common
You will then have a filesystem link from your main projects bower_components/bs-js-common folder to where the actual project repo lives. This lets you see live changes in both places.