A stock install of logwatch-7.4.1 does not produce any fail2ban output when run against fail2ban-0.8.13 logs. logwatch-7.4.0 worked fine against the same logs.
I was able to get the expected output by commenting out the following line in /usr/share/logwatch/default.conf/services/fail2ban.conf:
*OnlyService = fail2ban(|\..+)
My fail2ban.log file has entries in the format of:
2014-09-25 00:32:45,516 fail2ban.actions[28607]: WARNING [ssh] Ban 113.160.133.124
2014-09-25 00:42:46,176 fail2ban.actions[28607]: WARNING [ssh] Unban 113.160.133.124
The distributions package maintainer should ship a proper config file.