We have heard from someone we trust that the bark beetle treatment is 1) only a deterrent and 2) is only good for about 30 days and 3) is not effective for an tree that is already infested. Apparently there is some sort of treatment, involving injection of insecticide into the tree that might be effective but it requires significant irrigation of the tree which is illegal under the current drought conditions.
Best to call a real pro and get the straight skinny and a guarantee.