Yes, Wayne. I agree with your logic. At the same time, we can't forecast and avert such issues. Frankly, I'm not a fan of bonding building grounds via telephone cable sheaths for this very reason.

I'm not sure about how Canada's electrical code addresses this. The US electrical code (NEC) has become much more involved in this area over the past few years.

The NEC allows certain exceptions for the use of separate 'neutral' and 'ground' requirements as long as there is no other metallic connection between the buildings. This can be water, gas, conduit, telephone cable sheath, or anything else. In a perfect world, the ground potential differenence between two buildings is zero volts, but that never happens due to variations in soil conditions. There is always a difference.

Your situation is a classic example of the chicken or the egg. On one hand, bonding both buildings together via a cable sheath could easily result in a complete failure in the event of the electrical/grounding issue. On the other hand, having the cable at a possible different potential (voltage) with a floating end from the local ground could be a shock hazard. A shock hazard it a bit of an extreme, but it can happen.

It is really up to what the CEC has to say. How about making a call to the local inspection agency to get their feedback? That might be your best bet to cover yourself.

Ed Vaughn, MBSWWYPBX