I just heard of yet another diocese in which the Office of Worship has ordered all parishes to sing a commercial setting of the new Mass text for a period of one year - which means that every parish must buy music from a publisher and is effectively forbidden from using the music in the Roman Missal. Of course this is a huge subsidy for the publishers and a big cost to parishes that could otherwise use free music. It is also seriously problematic when a parish cannot on its own choose to use music from the Roman Missal. I don't even see how that could stand a serious canonical challenge - but of course the period that bans the chant will end by the time such a challenge even got off the ground.
A good history of this transition will have to have a chapter on these cases, with a thorough explanation of the precise circumstances that brought them about. So far, there is no firm empirical data on how often these circumstances have presented themselves. One knowledgeable person actually speculates that the entire hope of a national Mass setting (a wish of all Bishops in the English-speaking world) has been thwarted through these tricky methods.