For now Alliance buildings are:

Alliance Shrine: The Alliance Shrine increases the Alliance Dominance and keeps the Relic temporarily during cross-district events

Alliance Turret: When the Alliance Shrine is under attack, the Turret will take part in the battle. It also increases the Alliance Dominance boost.

Alliance Resource Mine: An Alliance Resource Mine is of large resource deposits, and you won't be attacked on it.

For details: ‘Alliance Building’.