Having a dedicated pair to use for DSL doesn't mean that a new wire must be placed. If there is extra pairs available in the existing wire then they can be used. A step-by-step post with pictures can be seen here:

Apartment Install

NOTE: Tampering with "Telco only" equipment may result in lose of service or fines. Telco equipment shown for illustrative purposes only.

This method uses a filter placed outside and makes use of one of the extra pairs in the existing wire.

FAQ by kadar