From the description, it sounds like the exterior conductors are unprotected service lateral. Based on that, a disconnect would be required at the point of entry into the structure. As to the 'distance' from the point of entry to the disco, 'closest to the point of entry'. As that is 'gray' or vague....it is the determination of your AHJ. 20' is not compliant IMHO.
As Tesla said, are the conductors POCO responsibility?? The answer varies by each POCO. I suggest that you contact the POCO before you get into anything.
