ssh -vT user@bitbucket.org
won't ever work.
Only git@bitbucket.org
can work.
As mentioned in "Use the SSH protocol with Bitbucket", a valid ssh url for BitBucket repos looks like:
git@bitbucket.org:accountname/reponame.git
You can change the remote origin url with a:
cd /path/top/your/repo
git remote set-url origin git@bitbucket.org:accountname/reponame.git