It does indicate application of additional facility rules (http://icsid.worldbank.org/ICSID/StaticFiles/facility/partD-chap01.htm but it applies to MANY cases.

It is usually applied where the parties agree to use the AF rules for arbitration (Schedule C, Ch. I Art. I) and if the dispute "do[es] not arise directly out of an investment," like where some bonehead won't give you a permit to actually build your mine.