That fusible link is what saves the building. Despite the fact that a maintained cross with power will effectively destroy the BET, it does it's job by having pairs that blow "open" to stop the direct metallic connection between the fault and the building.
Since the fusible link is either contained within the UL listed BET itself, or within the confines of a fire-retardant cable stub, what fails is a cable pair and any flame or spark is contained effectively.
Again, the fusible link is the proverbial (and intentional) weak link. It's understood that when it fails, the BET is shot. Lose a $1,000.00 BET, yet save a $1 million building, not to mention the potential personal injury or loss of life from a resulting fire. Remember, this cross with power can happen miles down the road, not just at the immediate premise.
