You are using very outdated version of podbot mm (and no longer supported).
Here is the info about latest supported version.
http://forums.bots-united.com/showth...?t=5714&page=2
All info about pb_bot_join_team was related to that version.
Of course - mp_autoteambalance has to be 0 - otherwise this setting is not affecting neither the team the bot wants to join.