hmmm…naw. Remember most Oxford applicants are cross-applicants I’m pretty sure. Then you get in where you fit in. In some very rare cases (which may become more common as the stats of the 2 campuses continue to converge-as in Oxford slightly or substantially increasing while main stays flat), Oxford may deny and main accept. And this is likely a fit issue because Oxford has no incentive to yield protect (it is not relevant for ranking purposes).
But when I say collaboration…I’m not talking like Ivies in a consortium type of way. I’m talking staff at at each campus likely directly being involved in admissions decisions.