There are ways to make this faster, but not everyone has the tools to do it. There are machines that can freeze the pipe to block water and there is a tool called JetSwet (may not have that spelled right for their trade name) that, once you have the water off, you can use that tool to block the water immediately. You'd use that to install an intermediate shutoff valve, then do the rest of your plumbing, while the rest of the building has water restored. You could cut the pipe and insert the JetSwet almost immediately after the pressure was off as it acts like a valve to hold the water back while you install a new valve. Once it is soldered in, you can remove the JetSwet, shut the new valve, then turn the water back on and then complete the rest since you now have a new, local shutoff. You just can't solder things while there is a constant drip of water in the pipes, and stopping it can take a very long time (or not).
You may be on the 11th floor, but if there are lots of floors above, it becomes a bigger unknown as HJ said. Think finger over the end of a straw...someone opening a valve above can release water that was trapped. Since valves are not all created equal, under vacuum, they may leak while not leaking under pressure, then, if someone has a leaky faucet or say toilet valve somewhere above you, it could leak for hours.
To give you an idea, here's the instructions for the JetSwet...
http://www.brenelle.com/index.php?type=how
Depending on the hourly rate, if he didn't have one, it might be cheaper to buy one and let him use it so he wasn't sitting around twiddling his thumbs (but, depending on the scope of the job, he may be able to prep other things while the water stops dripping.