The Jenkins service does not work for git repositories (it might for mercurial, I have not checked).
As a test I configured two services for a repository: //Email diff// and //Jenkins//. The //Email diff// services works perfectly: immediately after a commit I get an email with the full diff. The //Jenkins// services did not do anything. Looking at the apache logs for our (unsecured) Jenkins instance I can see that bitbucket does not attempt to do a POST (or GET or any other request).
I'm marking this as critical since the workaround is to configure polling in jenkins, which will increase the load on the bitbucket platform.