Sorry for the late answer but your last sentence shows that just maybe you are not sure yourself.  In all cases, there MUST be a shut off valve else water will just shoot out.  The question is if there is water in the pipes.  If the building does not have a sprinkler system, then water pressure from the BWS will not be sufficient.  Do you know how homes get their water pressure?  Do you know what a DRY Stand pipe is?   Let me know when you find out and I will let you know what I find out.