All traits will be made class-exclusive.
Adjustments will be made so that certain actions will only unleash their full potential when paired with traits belonging to the same class.

If it helps. My interpretation of this is that spells/abilities used cross class will be scaled down do to the lack of the class traits that are non-transferable to other classes.

thus in my understanding it would scale, but not to the same strength it would on the original class. I don't believe the spell itself is level related, you simply aquire the spell at said level.