I had the same question when we went through the process a few years ago. Disclosure: I have no special insight into what happens in admissions offices.
But now on the other side of it, I highly doubt it. They don’t have the time during admissions season to horse trade. There doesn’t seem to be a pattern like that in the results – some really talented kids don’t get in anywhere and there are others who get into a lot. I think they all only pick the kids they really truly want. Plus there are so many kids that they really truly want that they don’t need to compare lists. I think they instead use financial aid to woo the kids they really want. Plus, most schools don’t publicize their yield rates, so yield wouldn’t be a motivator.
That said, it is a small community, and they know each other. I can imagine that after April 10 they compare notes over a beer or two.