I like the idea, but I'm not sure that the savings would be worth the costs. The difficulty is that it is very hard to match the time of the accident to the cell phone records. The car's event recorder is not accurately time synchronized. The cost of equipping event recorders with time synch for gathering accident/cell relationships is too high for just research. If there was some significant monetary value, that could change this. But it needs to be more than just a change in fault assignment because insurers cover both sides.

For example, I've always liked the idea of enforcing seat belt laws with a mandatory $10K extra deductable on health payments for the person not wearing the seat belt. They get to pay some of the extra costs resulting from their decision not to wear a seatbelt. This is probably not all the extra costs, but if the level is too draconian the public will not accept a change like this. The insurers would become interested in cell records if there was an extra deductible paid by the driver in the event that they were contributing to the accident by talking on the phone at the time. Then there might be enough incentive.

As for your concerns on anonymous data, I routinely see effective anonymization. The problem is not technologies. The problem is taking the proper approach. Most people want to gather and mine a vast pool of anonymous data. That does not work. That is relatively easy to break. Good anonymization starts by determining what is the minimum data that must be collected to answer the question being asked, and removing everything else. This is the approach typically used in clinical drug trials, where the requirements for effective double blind analysis coincide well with the needs of anonymization. Breaking the anonymization of drug trial information cannot be done by a simple flip the switch. It takes several steps.

The clinical trials also design in a simple method for breaking anonymization when appropriate, which reduces the pressure to defeat the anonymization. If a trial investigator happens to notice an unrelated disease indication, there is an established series of trusted third parties, none of whom have complete knowledge, for getting a notification back to the correct patient and their doctor. There is less pressure to gather excess data because this does not benefit the drug sponsor, investigators, patients, or regulators. So privacy violations tend to be accidental, misunderstandings of procedures, or mistakes in determining the minimum data requirements for the study.