AppleCare has never covered user caused damage - it provides
protection against manufacturing defects. I do not know the provisions
of AT&T insurance so I cannot comment, but you should have been
given documentation when you signed up for the AT&T insurance or
find it on the AT&T website.
Do you have AppleCare or AppleCare+? Provisions are different and
details are at Apple.com
$199 US is the price for out of warranty replacement on an iPhone 4S.
Check with Speck to see if they provide any assistance/coverage for
using their case.
The Apple Care+ being sold now, for the iPhone 5 DOES include two "accident" incidents, though you must pay an additional $49. for each of those events.
I confirmed that includes drowning the phone or shattering the glass. It must be purchased within 30 days of the the iPhone 5 purchase and a Genius will have to inspect the phone prior to purchase. If puchased at the same time as the iPhone, no inspection is necessary.
Cost in the U.S. = $99.00 and Apple does label is "Apple Care+."
That is not totally true on the DOES part.
It depends on the extent of the damage.
A normal shattered glass would be covered under app+
A phone that has been ran over by a car or a phone that dropped and broke into a bunch of parts would not be covered. That's catastrophic damage and excedes the normal accidental coverage.