It looks as though the pressure has paid off. Ross McKitrick has emailed to say that he has now been invited to submit to the Interacademies Council inquiry into the IPCC.
Better late than never, I suppose.
I've also had an email from Marcel Crok, who has also been speaking to the IAC. Marcel's information seems to suggest that McIntyre will be contacted too, so this may well turn out to represent a small step forward.