Does Volvo pre-wire (as part of the total wiring harness arrangement) for options such as subwoofers and additional 12 V outlets in the 2001 models, or is the wiring only installed on the production line as specifically needed for factory installed options?

In V70s, there's a 12V outlet in the cargo area but that's it. No added wiring for a remote CD changer or other items like a sub BUT it's not hard to wire that stuff up either as long as the installer knows what he's doing.