My wife's company works in a separate building (leased) from the main one (100 yards away) in which the fire alarms are on separate systems. She has been told that if the alarm goes off in one building they must phone the other. Surely this cannot be right? What if they don't hear the phone and the assumption is made that the building is unoccupied, and it may not be? 

They say the alarms cannot be connected. In this day and age, really?

Surely all people need to evacuate ASAP and not make a phone call? They won't do a site check to see if anyone is there.

If they are physically separate they don't usually need to both evacuate hence why the systems are not linked.

They can be connected, massive industrial sites of multiple buildings have had connected site alarms since the 1950's! What they mean is they don't want the cost of doing so.