If they need to do a public bidding because they did not planned to implement a service like yours soon, the whole process takes up to a year.
Cities all have a different tender process/rules. Most ask you to have an insurance of up to a 5 millions by event adding mostly 10/15k in expenses.
There was a lot of interest, but cities did not have the cash on hand to pay for my services. I was billing up to 100k/city/year.
Mostly, if you have a product that can be paid for by the federal government or the state, they will buy it in an heartbeat. Eg: if it helps handicapped people.
The good: the LTV is really long, 10+ years. Try to find a champion in the town hall, that person will help you setup your offer so that the different branches of the city are happy.
Also, overcharge. Cities love personnal support. You will spend a lot of time on the phone, talking to real people.
For more info, write me an email at bobberkarl(at)gmail.com