Mandated? You must be kidding!
MANDATED that your car can tattle on you? Because that what putting a cell modem in the car means. It won't just be phoning in when the airbags deploy, it will be constantly telling the towers where it is (because that is how cellular works - it cannot wait until it needs to make a call to check in), and I'll bet a week's salary that it will be able to dump all the ODB-II data over to the cell network on demand as well, so they can check up on how fast you are driving (and likely work out how many people are in the car, based upon engine load and suspension data). Likely they will also require the system to be able to shut the car down remotely, as well.
I don't dispute that having the ability to make a call on a collision is a good thing - but what is wrong with my car using my existing phone, and making the call be a proper emergency call, which will notify me (by my phone playing the "emergency call in progress" tone) that it is happening. That way, if I am *not* sucking air-bag, I can ask "OK car, why for are you making a phone call?"
That is one of the reasons I WILL NOT buy a GM car here in the US - you have to fight like hell to NOT have OnStar installed by default.