Only when the power is 60 or below. For example, Magnitude 5 is powered up, Magnitude 6 is powered up, and Magnitude 7 is not powered up.
Source: Experience.
EDIT: Sorry if this left confusion, I thought it was clear enough. What is said is exactly what I mean: If the base power is 60 or below, then the move is boosted. My magnitude example was supposed to clear this up. If a move like rollout hits with 60 or below, then it's boosted. As soon as the base damage exceeds 60, it will no longer gain the boost. The same goes for pursuit, meaning that if Pursuit's base damage doubles on the switch, then the new base power 80 is not boosted.