Perhaps I've lived too sheltered a life but I've never heard of a separate charge for 911 calls. Admittedly, I'm in the South and perhaps things are different down here. Here, there is a monthly fee (a dollar per phone line, I think) added to the phone bill to help finance 911 operations. The per-call fee might deter people from reporting activity they see while they're driving or even walking. I would think that a singe fee collected by he service provider and paid to the government on a regular basis would be simpler way to collect the revenue.
If I'm not mistaken, 911 calls are actually routed to a regular phone number that is not generally publicized. What happens if the person calls that phone number instead? Either call goes to the 911 center and on most systems, the call-taker has no idea which phone number the caller dialed. I usually dial the non-911 number from my cell phone so the phone is not "locked" to maintain the connection to 911 for a certain period of time (I don't use a landline at home anymore.)