Yeah, I'm going to try to get back into reading and reviewing missions again. >_>
Your writing style does a good job of being very succinct, and getting straight to the point without a lot of extra words cluttering up the sentences. This is especially useful in missions for getting across info from the badfic without copy-pasting huge blocks of text, and you make good use of that here. There were a couple of potentially interesting spots that I feel you could have gone into more detail on—namely, the canons initially arriving in the present, and Holmes making deductions about the profession of a woman in the restaurant, which I feel could have been good moments for the agents to look at with a critical eye, as they would especially be indicators of how out-of-character Holmes was. Then again, I don't know if the original fic presented those scenes with enough material for you to really do anything with.
I'm not sure the canons themselves were quite out-of-character enough to be treated as replacements, although I know that's a subjective thing for each PPC author. In particular, the sentence, "Without being told, Holmes easily lied and said that his last name was Jones," seems to indicate that you felt Holmes would need guidance in having to mislead someone, but (at least in the novel canon; I haven't seen the movies) Holmes is a master of disguising his clothing, voice and demeanor to hide his identity. He would certainly have no trouble coming up with a fake name, especially since the plan to fool the mothers had been thought of in advance.
I'm also a bit confused by the final charging scene. I understand Holmes and Watson being killed, since you're treating them as replacements, and I'm glad your agents neuralyze the mothers and return them to their regular lives, but where did the two daughters go? It seems to me that, if the mothers are being treated as "canons" and returned to their lives, their daughters should be, too. And I rather had the impression that the flat the daughters was living in was their actual home, before the fic started, so wouldn't they just get neuralyzed and stay there?
I do like the last line, "'Come on, we have paperwork to fill out.'" I usually think of agents writing up mission reports that resemble our missions when they report said mission, but I like the idea that these agents are just going to file ordinary paperwork when they get home, and that they both need to participate. A tiny little detail, that makes a lot of sense.
—doctorlit, hoping to have a bit more time at home from now on