Brez63,
Good question. Instead of the company listed on a few exchanges, same company share everything, this is different.
ERHC, now listing on the OTCBB will have controlling interest on a subsidiary on another exchange. Since ERHC will own most the subsidiary after the IPO ( remember, you only put a portion of the shares of a company up for the IPO ) AND, if that subsidiary gains in value, then ERHC's pps gains as well by extension, since ERHC still owns most the sub even after the IPO.
Hope this helps.
Red