"It doesn't matter how fast you respond when you respond to the wrong location," said Councilman James Vacca during a hearing on Thursday.
Council members peppered city officials with questions about the new system.
There have been huge cost over-runs and embarrassing examples of 911 dispatchers sending firefighters to the wrong place.
But the mayor has strongly defended it.
One big change? Instead of two separate call takers for police and for fire, it's done by one.
"So from an outset it saves time, valuable time, because seconds count. You only have to talk to one person not two, and that's just a basic premise," Deputy Mayor Ed Skyler said.
The mayor's team touted the system as one that led to a big drop in fire response time and that saved lives, but the firefighters union cast doubt on every aspect of the 911 upgrade.
"It is a disgrace. The system has many failures in addition to the biggest one. They are lying about response time," Steve Cassidy of the Uniformed Firefighters Association said.
The change has led to turf wars between police and fire. Some in the audience hissed at one comment about how good a job police are doing taking fire calls.
"Can a police call taker do as good a job as a fire call taker? We believe the answer is yes," Skyler said.
City officials also revealed they're looking at the possibility of some day having one person answer not just police and fire calls, but also emergency calls to EMS. Depending on who you ask, that'll either make 911 more efficient or it's a recipe for disaster