ISO 3166-1 defines "BC" prefix as free, if ISO 3166/MA was to assign "BC" to the Bitcoin Community, it could open other possibilites too (BCX?). It is however unheard that an ISO entity assigns a prefix to a community.
Indeed. Even the EU country code which makes EUR a valid currency code was reluctantly assigned as an "exceptional code" and the EU represents over 500 million people!
http://en.wikipedia.org/wiki/ISO_3166-1_alpha-2#Current_codesThe path of least resistance is with an unused X-code...