I spent hours and hours to get access via sourcetree to the bitbucket with ssh key without luck.
> git remote -v
=> shows currently origin ssh://bitbucket.org/...
test of the ssh key (loaded)
> ssh -T git@bitbucket.org
=> authenticated via ssh key. You can use git to connect to Bitbucket. Shell access is disabled
In sourcetree > account > I can connect the account and I also see the ssh key used.
Auth type: OAuth; protocol: ssh
When checking in sourcetree project settings > remotes > add > selecting the repos on my account doesn't show any repos.
For now I start using tower app as this seems to work well.