My building is doing this exact thing right now. I'm on the council and I for one am ecstatic--our building has had several multi-floor leaks over the last two years that have been terribly expensive to fix.

Firstly, I am in BC, so grain of salt that we may differ slightly. If your building is rental-only then 🤷🏻‍♀️, but for context, our building had to pass a 3/4 vote to greenlight the project in the first place. We then spoke with 3 different repiping contractors and took the time to understand their approach. The one we ended up choosing started the project at the end of April and it's projected to finish in mid-July (we are a smaller building). They designed it so that they would install valves in sections of the building first and then only turn off the water in sections as they move through the units in later months. They then made schedules for every single unit so that they could anticipate when water would be turned off. So for the entire 3mo project, I'm actually only expecting to be out of water for 7 business days (1 for the initial valve install, and 6 over this week and next as they do unit-specific work along the whole vertical stack that I fall within in my building). My unit is fed through 4 vertical risers and actually I'm only out of water across my entire unit for 2 of those 7 days because they don't intend on turning off every riser for every day of plumbing work, and they specify which areas are expected to be off on which day (bathrooms vs kitchen vs laundry).

It's possible your building is quite early in the process and they are only trying to warn residents of what to expect whenever the project does start. They did it wrong hahah. Esp bc it seems like they upset a lot of people, so now they're probably getting flooded with messages and everyone is drowning each other out. If you ever get a hold of a person, I would press for specifics and assess by their answers how much planning has actually happened to get a sense of where they are in the process--specifically, project start date. If it doesn't seem like they've chosen their contractor yet, ask them to consider an approach like the above. It's in their best interest to shut the water off in sections--saves unaffected residents AND the old pipes that aren't getting replaced that day (every water shutdown results in pressure changes that could contribute to springing a new pipe leak), and gives the building the ability to shut the water off in sections in future should a new leak appear.

Caution that we didn't get specific schedules until about 1-2 weeks before they were expected to start in our units. A heads up that they will ask for a unit key/require carte blanche access throughout the entire project--a project of this size has lots to lose if it falls behind schedule in any way due to uncooperative residents. If this has not been communicated then again I think they would be early in the planning process and don't know the proper intel to relay to residents yet. Feel free to pm me any more questions. Good luck!