What do you mean by "as long as the signal makes a transition "?
Does the flow meter output a digital or analog signal?
If those threads are BSP/Straight and your piping is NPT, you'll also need couplings. Or a lot of dope and washers. Also those cheap Hall effect sensors can really restrict flow. May not want to do that off of the main line. Good luck.
if you were to look at the existing city meter, there should be a way to connect to it to get a reading. there are aftermarket sensors that attach to the glass and 'look' at the needle and report the needle spinning.you can buy a true water meter for under $100 USD Since you have to cut the pipe for any installation i would look at cutting the pipe inside of the building and not outside. find the diameter of the pipe for the size so you can match size for size. Meters are often sized by the pipe .
The city has every right to remove any object that they deem as an obstruction on their property... just fair warning.
Thanks but that's totally not how it works here. They barely have analog meters, requesting anything is out of the question. I mean, I could request it, but wouldn't be in their top 99th percentile of priorities.