Contracting to water company

Ok like the title says, my local water co. Approached me about the possibility of contracting with them to handle all water line break repairs, meter installs, basically everything they do except reading meters and monitoring the towers.

I have the equipment, they will supply me all maps( showing locations, line sizes, valve locations, etc.)
I have a good working relationship, I have helped them before when they needed an excavator, or just in a situation they neede help.

I live just a few miles from the shop, and know the area they cover. My question is what is common practice before we set down with the board. Time and material, contract price per break, ?

There is a few other districts that do this but I don't know how they have it set up. Any body have experience doing this? Just putting it out there to see what other parts of the country do.

Thanks for looking

Contracting to water company