Our street is made up of small terrace blocks (3 or 4 houses in each) and each block has a shared mains tap, so I think it's quite common. We didn't discover this until the plumber came to fit our new boiler, so we had to tell the neighbours they'd be without water for a few hours. But as it turned out, the first job he did was fit a shut-off valve inside the house, which took him a matter of minutes, and then he could turn the mains back on again without affecting our house. Hopefully your plumber can do the same thing, then the shared one only needs to to be turned off for a short time.