Conductance per unit length
Would it be possible to measure a resistance between the two wires?

Unless you can somehow deliberately short-circuit the other side of the transmission lines, you will not be able to measure the total (DC) resistance of these wires and as a result the resistance per length. Even if there is some kind of parasitic path between the two wires, I think it is safe assume there is no way to find out where it occurs, and how large the resistance of that leakage path is without prior knowledge, making the problem effectively unsolvable.
You may have a better chance of characterizing these transmission lines (if that is your ultimate goal) using a Time-Domain Reflectometer (TDR). I think it's safe to assume they're pretty expensive though, and they require some knowledge about transmission lines and voltage/current waves to interpret (I've only built and characterized the setup of a TDR in an academic setting).