"USUALLY"!!!
It would be far more beneficial if you would cite some aspect of the Revised Statutes, DMV handbook or web information, or something that has standing in merit. So far part of your analysis, if true, about what lanes can be towed in has not been supported with legislative citations or quotes from any official source. It appears in the statutes that regardless of how many lanes are in the same direction only the slow lane and the adjacent lane can be used for towing except where there is specific signing that allows for lanes three or four to be used and that would normally be at a left exit intersection/off ramp. But, hey, you live in California, maybe you know more than the rest of us. Incidentally, for your information, that part of the towing law was added after the eighteen wheelers felt it their domain to hog the fast lane regardless of traffic or speeds. So the legislature added the lane towing section to the statutes.