If you were SCO, where would you host your investor relations site?

With IBM, of course.

Sequent [reported as the owner of the netblock] is an IBM subsiduary, and part of its IP address ranges are used by IBM Global Services for their hosting operations.

% ping ir.sco.com
PING client.shareholder.com (170.224.5.43): 56 data bytes

ir.sco.com is a virtual host on an investor relations system run by shareholder.com and it's plausible that SCO did not previously know the ultimate hosting location, nor IBM the identity of shareholder.com's clients.