A line from the film Michael Clayton:
Barry's taking over on U/North. We got a lot of grovelling to do.
Barry is an associate at a law firm, and U/North is a case/client. I would expect take over a case/client. Google Books show a limited number of instances of take over on, most results false positives. Is "take over on" idiomatic/commonly said? Is on here a preposition or part of the whole phrasal verb?