Someone in Number 10 writes what they think is a clever answer to some kind of soundbite they want to get out, then thinks of a question, and passes it to a passing MP to ask?
The difficulty would be that the questions* go into a ballot, as there are many more questions than the 15 allowed, so there's no guarantee that the clever answer would ever be needed.
Also, according to the parliament website, many MPs opt for a generic "engagements" question (so common that they just have to tick the E box) so that they don't have to submit the text of their question.
And, yet further, members can ask totally unprepared questions simply by standing up and catching the Speaker's eye.
So, the chances of the Cabinet, or anyone else, sitting around planning how the PM should answer questions are pretty remote. Still, I expect you knew all this as you say you know enough about parliamentary procedures.