I'd tend to agree that the line might be connected to an alarm system. Maybe someone just grabbed one or two lines and ran them into the nursing home's alarm system. I don't think it's the telco routing misdialed calls to 911. I spent a few years involved with C.O. translations. I never saw this done. It could be a hot dial situation where the line is translated to dial 911 or another emergency number when it goes off-hook.

Gary