The answer is Scenario (b) (i.e. Technician won't apply).
This is because
For moves with variable base power, Technician will only apply if the base power is 60 or less when used. Thus, Pursuit will not get a Technician boost if the opposing Pokémon switches and Pursuit's base power doubles to 80. Similarly, if a move like Avalanche is used by a Pokémon previously damaged in the same turn, which doubles Avalanche's base power to 120, then Technician will not be applied.
I would count Acrobatics as a move with variable base power, much like pursuit. As such, it will only be boosted by Technician if the user is holding an item.