According to the article, she got the bill because she was not a resident of the town where the accident happened. And it's a bill to recover costs, not a fine - the article sounds very much like she still would have gotten the bill if it was an emergency.

CTV News Toronto reached out to officials in London, who confirmed "The City of London charges fees when the London Fire Department responds to a call or incident on any roadway within the city that involves a vehicle owned by a resident from outside of London." "This fee is included in the City of London’s Fees and Charges By-law, and it is intended to recover costs when services are provided to a non-London resident," the spokesperson said.

The article you posted suggests it was because she was from a different municipality?