Quote from Dirtyankle " I would really prefer not to cut the wall but I think if I don't the homeowner may exterminate the rest of the colony."
This is where you tell them, most attempts at spraying colonies fail.
Also, even more importantly, if they are sprayed, and not killed off, the colony could move between the brick and the vapor barrier (blackboard) if your houses are built anywhere like our brick houses are, and in that space, there are no boundaries, as in an enclosed wall space, where they probably are now.
How do I know this? Because I have seen this many, many times and its not a pretty sight and the job of removing bees and honey off of bricks and mortar becomes a nightmare.
Tell them with confidence, that the bees and comb needs to come out, or a trap out needs to be done. Talk to Iddee about trapouts and read his posts about trap outs on here.