After some more searching, a good discussion is posted here.

Notably:

Despite the restrictions on who can view quotations, the Expert Market does not impose restrictions on who can trade securities. Rule 15c2-11 governs a broker’s ability to submit, publish or distribute quotations (i.e. bids and offers) in OTC securities. The Rule does not apply to the underlying transactions or the ability of an investor to buy or sell a security.

(emphasis mine)