I extend T1s in malls all the time. Telco drops them at the mpoe and we take it from there. I try to run a dedicated line for each one but if customer wants to use the house pairs then we try it out. If it works then we leave them, other wise we will install single pair T1 extenders that will push it to 3.5 miles or run a cable, this all depends on length. If running a cable will execced the cost of the extenders or length, we go with extenders as they run just under 1k. And have never had an issue with this. Label and mark all pairs used with customer info for referance later and for others coming in and doing service work for other customers later.

"It works on our end so it must be fine."