Yes. The reposman.rb script is explicitly meant for this purpose.
Usually it is done calling the above script on a cronjob i.e:
10 * * * * root ruby /root/redmine-1.0.0/extra/svn/reposman.rb --redmine-host http://my.redmine./ --svn-dir /data/svn/ --url my.svn.server --key=mykey --owner apache --verbose >> /var/log/reposman.log
However, mercurial does not have an equivelent implementation as the above is for SVN (http://www.redmine.org/boards/1/topics/575). It is possible to write your own hooks to accomplish this. If you don't mind modifying the Redmine core you can use the information here as very minimal source of approach on the issue:
With above method you could call a shell script containing the commands you would normally use to create a repository. This is fully customizable. (A shell script is just a file with execute permissions containing commands as you would type them on the command line). Basically using that guide for creating a repository you would call a script which created a directory by the name of the project identifier
cd into that directory and then run
hg init You could then use mysql to add the repository automatically to the project identified by the project identifier.
A more elegant solution would be to use the above with native Redmine hooks in a plugin or creating copies of the modified pages in a plugin which would automatically override the Redmine core - http://www.redmine.org/wiki/1/Hooks
If you need to do anything with the database the below is helpful: