"...most things that will bring down line #1 will also bring down line #2. They are probably traveling the same path to the same equipment in the same central office."
Let me try to say this in the gentlest and kindest way possible...
"WRONG"
If that were the case, then my final 10 years performing cable maintenance were a big waste of time and a million dollars of the company's money.
Imagine if the phone company had realized that all the lines take the same "path" to the CO. They could have eliminated all those cables, manholes, poles, splice cases, terminals, LARP circuits, air supplies, and massive MDF's.
