Ranger, I can't see the privately owned European clubs, releasing any more players than they have to, for a world cup, so I doubt that they could be enticed into releasing players for a team to represent a country not selected by that country's union.
As for the IRB's stance on things, they (like the NZRU) are about to go into negotiations, so they are trying to look as strong as they possibly can ... it will be interesting to see who supports who ... I think the threat of withdrawing IRB money, may persuade some unions not to support New Zealand (the island nations)
... I think the player's association might have a deciding factor in determining the outcome of this (and other) issue(s).