A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
A player, 30 August 2013
Plains of the Maiden After you destroy a province or army in battle resolution as the Attacker: Gain Honor equal to the number of your Battle Maidens at the current battlefield.
Shiotome Halls After a battle's resolution ends, if a province or enemy army was destroyed during it and you control a unit in the winning army: You may gain Honor equal to the number of Battle Maidens in that army.
As far as I know, Plains of the Maiden triggers once for destroying an army and again for the destroying the province.
Does Shiotome Halls (and by Extension, Tadaji Sensei) also trigger twice if you destroy both an army and province during the same resolution?
Alex Jones (rules official), 30 August 2013
Plains of the Maiden After you destroy a province or army in battle resolution as the Attacker: Gain Honor equal to the number of your Battle Maidens at the current battlefield.
Shiotome Halls After a battle's resolution ends, if a province or enemy army was destroyed during it and you control a unit in the winning army: You may gain Honor equal to the number of Battle Maidens in that army.
As far as I know, Plains of the Maiden triggers once for destroying an army and again for the destroying the province.
Does Shiotome Halls (and by Extension, Tadaji Sensei) also trigger twice if you destroy both an army and province during the same resolution?
No.
Plains of the Maiden triggers off the effects "destroy an army" and "destroy a province". If you destroy both in one battle's resolution, the trait will trigger twice.
Shiotome Halls (and Tadaji Sensei), on the other hand, triggers at a step in the battle sequence, so it can only trigger once per battle.