It is probably a cost-saving measure rather than an attempt to force him to leave the job.
Because he had the benefit of the car for 3 years and it was provided under a verbally agreed arrangement, I'd be inclined to claim that it is an implied term of his contract that he has a car.
If the company wishes to change this then they can, by consultation, but it doesn't sound like any consultation has occurred. Even if they do change the contract, the company should be giving him at least his notice period's worth of time that the change is occurring - and this will be more than two weeks (it is probably 4 weeks notice?).
So I would raise a grievance with the company, stating that I consider it to be an implied term of my contract that I enjoy a car with the job, I am willing to discuss the matter to find out why the company wishes to change the contractor, but that at present the company seems to have unilaterally decided the change the agrreement without any consultation and not giving me notice.
If the company, as part of the grievance process, claims it wants to save money, perhaps by prepared to agree to be slightly smaller car.
Is he the only one impacted? Are there other cost-saving measures going on around the patch?
No doubt Tony W will have an valued view on this - if he sees the question.