If the foe Pokémon uses Pursuit on the same turn Volt Switch is used, Pursuit will deal normal damage if the foe is faster, or double damage if the foe is slower than the user.
Note: This also applys to U-Turn.
Source: Bulbapedia/ Volt Switch
Baton Pass will not trigger Pursuit.
Source: Bulbapedia/ Pursuit
For Circle Throw, it has a decreased priority of -6. Pursuit has a priority of 0 when noone is switching out. That means Pursuit would attack before Circle Throw can throw someone out.