Installing the Mail gateway is not difficult, but requires some modest system administration experience. Because of the group-membership security requirement for BATTS, it's simplest to create a user who is a member of the batts group. On my system, I created a user named trouble; if this user will not by default receive mail sent to the return address you configured in the above configuration files, you should create an alias that points at this account.
Most Sendmail installations have smrsh (Sendmail Restricted Shell) configured. This requires that programs which may be executed by users be stored (or symbolically linked to) in the smrsh directory. On my Linux system, this is /etc/smrsh, but this may differ on other Unix flavors. From that directory, create a symbolic link to the ticket-via-email script. On my system, this may be done as follows:
pushd /etc/smrsh ln -s /usr/local/bin/ticket-via-email ticket-via-email popd
While it may be possible to use an alias in /etc/aliases and have the ticket-via-email script setgid to the BATTS group, my gut feeling is that this would be less secure than creating another user. I have no real evidence for that assertion, however.
At this point, BATTS is installed on your system. Send a test ticket in via the e-mail gateway and see that everything performs as expected.