My employer's business number was called. The caller identified himself as an employee of the Seattle Fire Department and said it was related to business, but did not verify if he was pursuing anything work related.
I accidently called 911 on my cell, this is the number they called back from to see if everything was ok. I am pretty sure its just one of many operators numbers set to call on hung up emergency calls.
I got a call from this number regarding the city of Seattle P-Patch (community garden) program, but in the message they left (if it is important, they will leave a message!), they gave me a different number to call. Based on this and the other comments here, I would say that this is just a general city of Seattle outbound number for a variety of city things. Basically, I would say that if you do not reason to believe the city of Seattle is calling you, let them leave a message.