The main rule that provides that employee benefits have to be included in income looks at whether benefits are received as a result of employment. The standby charge rules are really like a subset of those rules that calculate how you determine the employment and how you determine the amount of the benefit.
I don't think this change is creating any new obligations on taxpayers. It's really just eliminating a loophole that existed because of the fact that the car had to be provided by the employer or someone related to the employer. It's simply eliminating the ability for employers to enter into some sort of arrangement where they have a non-related person provide the vehicle and then avoid the employee having to pay tax on the standby charge.