Normal ssh daemons have the ability to define the MaxStartups parameter to configure how many unauthorized connections are allowed in one second.

Question: Is there a similar parameter available in Bitbucket to secure the git shh service against brute force attacks or is there another method available or automatically in place to prevent brute force attacks?

There is an open question about using MaxStartups with mina-sshd (the library used for Bitbucket's SSH daemon).