Well, in your example for the issue, if that car was provided by company B and is not related to company A, then it wouldn't have been picked up under the current rule. Now, the rule would look at whether that car is being provided by company B to the employee of company A as a result of or a consequence of the employee's employment by company A.
Instead of looking at the relationship between company A and company B, you'd be looking at the sorts of reasons why that car was provided by company B to the employee of company A to determine whether that was done as a consequence of that person's employment.