All the Minor Faction's default units and structures switch to your side but as you don't own them, they are only willing to go so far to help you out.Your Envoy must continue its Goodwill mission to maintain the Minor Faction's allegiance (i.e it has to continue to channel the ability).The enemy Envoy must be destroyed or forced to retreat. Envoys cannot send Goodwill missions to Minor Factions that are aligned with enemy players.In a hostile environment an Envoy can use its 'Diplomatic Immunity' ability to secure the approach but its a limited duration ability so make sure no 3rd party enemies are there to disrupt you.By default Minor Factions are hostile to you but you can use an Envoy's Goodwill mission to convince them to join your side.

Every game will have a different combination of Minor Faction types and locations.